The Enzyme Database

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EC 1.1.1.306     
Accepted name: S-(hydroxymethyl)mycothiol dehydrogenase
Reaction: S-(hydroxymethyl)mycothiol + NAD+ = S-formylmycothiol + NADH + H+
Glossary: mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy-α-D-glucopyranosyl]-1D-myo-inositol
Other name(s): NAD/factor-dependent formaldehyde dehydrogenase; mycothiol-dependent formaldehyde dehydrogenase
Systematic name: S-(hydroxymethyl)mycothiol:NAD+ oxidoreductase
Comments: S-hydroxymethylmycothiol is believed to form spontaneously from formaldehyde and mycothiol. This enzyme oxidizes the product of this spontaneous reaction to S-formylmycothiol, in a reaction that is analogous to EC 1.1.1.284, S-(hydroxymethyl)glutathione dehydrogenase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 192140-85-5
References:
1.  Misset-Smits, M., Van Ophem, P.W., Sakuda, S. and Duine, J.A. Mycothiol, 1-O-(2′-[N-acetyl-L-cysteinyl]amido-2′-deoxy-α-D-glucopyranosyl)-D-myo-inositol, is the factor of NAD/factor-dependent formaldehyde dehydrogenase. FEBS Lett. 409 (1997) 221–222. [DOI] [PMID: 9202149]
2.  Norin, A., Van Ophem, P.W., Piersma, S.R., Person, B., Duine, J.A. and Jornvall, H. Mycothiol-dependent formaldehyde dehydrogenase, a prokaryotic medium-chain dehydrogenase/reductase, phylogenetically links different eukaryotic alcohol dehydrogenase's - primary structure, conformational modelling and functional correlations. Eur. J. Biochem. 248 (1997) 282–289. [DOI] [PMID: 9346279]
3.  Vogt, R.N., Steenkamp, D.J., Zheng, R. and Blanchard, J.S. The metabolism of nitrosothiols in the Mycobacteria: identification and characterization of S-nitrosomycothiol reductase. Biochem. J. 374 (2003) 657–666. [DOI] [PMID: 12809551]
4.  Rawat, M. and Av-Gay, Y. Mycothiol-dependent proteins in actinomycetes. FEMS Microbiol. Rev. 31 (2007) 278–292. [DOI] [PMID: 17286835]
[EC 1.1.1.306 created 2010 as EC 1.2.1.66, transferred 2010 to EC 1.1.1.306]
 
 
EC 1.2.1.66      
Transferred entry: mycothiol-dependent formaldehyde dehydrogenase. Now EC 1.1.1.306, S-(hydroxymethyl)mycothiol dehydrogenase
[EC 1.2.1.66 created 2000, deleted 2010]
 
 
EC 1.8.1.15     
Accepted name: mycothione reductase
Reaction: 2 mycothiol + NAD(P)+ = mycothione + NAD(P)H + H+
Glossary: mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy--D-glucopyranosyl]-1D-myo-inositol
mycothione = oxidized (disulfide) form of mycothiol
Other name(s): mycothiol-disulfide reductase
Systematic name: mycothiol:NAD(P)+ oxidoreductase
Comments: Contains FAD. No activity with glutathione, trypanothione or coenzyme A as substrate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 252212-92-3
References:
1.  Patel, M.P. and Blanchard, J.S. Expression, purification, and characterization of Mycobacterium tuberculosis mycothione reductase. Biochemistry 38 (1999) 11827–11833. [DOI] [PMID: 10512639]
2.  Patel, M.P. and Blanchard, J.S. Mycobacterium tuberculosis mycothione reductase: pH dependence of the kinetic parameters and kinetic isotope effects. Biochemistry 40 (2001) 5119–5126. [DOI] [PMID: 11318633]
[EC 1.8.1.15 created 2002]
 
 
EC 1.11.1.29     
Accepted name: mycoredoxin-dependent peroxiredoxin
Reaction: mycoredoxin + ROOH = mycoredoxin disulfide + H2O + ROH
For diagram of reaction, click here and for mechanism, click here
Other name(s): ahpE (gene name)
Systematic name: mycoredoxin:hydroperoxide oxidoreductase
Comments: Peroxiredoxins (Prxs) are a ubiquitous family of antioxidant proteins. They can be divided into three classes: typical 2-Cys, atypical 2-Cys and 1-Cys peroxiredoxins [1]. The peroxidase reaction comprises two steps centred around a redox-active cysteine called the peroxidatic cysteine. All three peroxiredoxin classes have the first step in common, in which the peroxidatic cysteine attacks the peroxide substrate and is oxidized to S-hydroxycysteine (a sulfenic acid) (see mechanism). The second step of the peroxidase reaction, the regeneration of cysteine from S-hydroxycysteine, distinguishes the three peroxiredoxin classes. For typical 2-Cys Prxs, in the second step, the peroxidatic S-hydroxycysteine from one subunit is attacked by the ‘resolving’ cysteine located in the C-terminus of the second subunit, to form an intersubunit disulfide bond, which is then reduced by one of several cell-specific thiol-containing reductants completing the catalytic cycle. In the atypical 2-Cys Prxs, both the peroxidatic cysteine and its resolving cysteine are in the same polypeptide, so their reaction forms an intrachain disulfide bond. The 1-Cys Prxs conserve only the peroxidatic cysteine, so its regeneration involves direct interaction with a reductant molecule. Mycoredoxin-dependent enzymes are found in Mycobacteria. Following the reduction of the substrate, the sulfenic acid derivative of the peroxidatic cysteine forms a protein mixed disulfide with the N-terminal cysteine of mycoredoxin, which is then reduced by the C-terminal cysteine of mycoredoxin, restoring the peroxiredoxin to active state and resulting in an intra-protein disulfide in mycoredoxin. The disulfide is eventually reduced by mycothiol.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, UM-BBD
References:
1.  Wood, Z.A., Schröder, E., Harris, J.R. and Poole, L.B. Structure, mechanism and regulation of peroxiredoxins. Trends Biochem. Sci. 28 (2003) 32–40. [DOI] [PMID: 12517450]
2.  Hugo, M., Turell, L., Manta, B., Botti, H., Monteiro, G., Netto, L.E., Alvarez, B., Radi, R. and Trujillo, M. Thiol and sulfenic acid oxidation of AhpE, the one-cysteine peroxiredoxin from Mycobacterium tuberculosis: kinetics, acidity constants, and conformational dynamics. Biochemistry 48 (2009) 9416–9426. [PMID: 19737009]
3.  Hugo, M., Van Laer, K., Reyes, A.M., Vertommen, D., Messens, J., Radi, R. and Trujillo, M. Mycothiol/mycoredoxin 1-dependent reduction of the peroxiredoxin AhpE from Mycobacterium tuberculosis. J. Biol. Chem. 289 (2014) 5228–5239. [PMID: 24379404]
4.  Kumar, A., Balakrishna, A.M., Nartey, W., Manimekalai, M.SS. and Gruber, G. Redox chemistry of Mycobacterium tuberculosis alkylhydroperoxide reductase E (AhpE): Structural and mechanistic insight into a mycoredoxin-1 independent reductive pathway of AhpE via mycothiol. Free Radic. Biol. Med. 97 (2016) 588–601. [PMID: 27417938]
5.  Pedre, B., van Bergen, L.A., Pallo, A., Rosado, L.A., Dufe, V.T., Molle, I.V., Wahni, K., Erdogan, H., Alonso, M., Proft, F.D. and Messens, J. The active site architecture in peroxiredoxins: a case study on Mycobacterium tuberculosis AhpE. Chem. Commun. (Camb.) 52 (2016) 10293–10296. [PMID: 27471753]
[EC 1.11.1.29 created 1983 as EC 1.11.1.15, part transferred 2020 to EC 1.11.1.29]
 
 
EC 1.20.4.3     
Accepted name: mycoredoxin
Reaction: arseno-mycothiol + mycoredoxin = arsenite + mycothiol-mycoredoxin disulfide
Glossary: mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy-α-D-glucopyranosyl]-1D-myo-inositol
Other name(s): Mrx1; MrxI
Systematic name: arseno-mycothiol:mycoredoxin oxidoreductase
Comments: Reduction of arsenate is part of a defense mechanism of the cell against toxic arsenate. The substrate arseno-mycothiol is formed by EC 2.8.4.2 (arsenate:mycothiol transferase). A second mycothiol recycles mycoredoxin and forms mycothione.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Ordonez, E., Van Belle, K., Roos, G., De Galan, S., Letek, M., Gil, J.A., Wyns, L., Mateos, L.M. and Messens, J. Arsenate reductase, mycothiol, and mycoredoxin concert thiol/disulfide exchange. J. Biol. Chem. 284 (2009) 15107–15116. [DOI] [PMID: 19286650]
[EC 1.20.4.3 created 2010]
 
 
EC 2.3.1.189     
Accepted name: mycothiol synthase
Reaction: desacetylmycothiol + acetyl-CoA = CoA + mycothiol
For diagram of mycothiol biosynthesis, click here
Glossary: desacetylmycothiol = 1-O-[2-(L-cysteinamido)-2-deoxy-α-D-glucopyranosyl]-1D-myo-inositol
mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy-α-D-glucopyranosyl]-1D-myo-inositol
Other name(s): MshD
Systematic name: acetyl-CoA:desacetylmycothiol O-acetyltransferase
Comments: This enzyme catalyses the last step in the biosynthesis of mycothiol, the major thiol in most actinomycetes, including Mycobacterium [1]. The enzyme is a member of a large family of GCN5-related N-acetyltransferases (GNATs) [2]. The enzyme has been purified from Mycobacterium tuberculosis H37Rv. Acetyl-CoA is the preferred CoA thioester but propionyl-CoA is also a substrate [3].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Spies, H.S. and Steenkamp, D.J. Thiols of intracellular pathogens. Identification of ovothiol A in Leishmania donovani and structural analysis of a novel thiol from Mycobacterium bovis. Eur. J. Biochem. 224 (1994) 203–213. [DOI] [PMID: 8076641]
2.  Koledin, T., Newton, G.L. and Fahey, R.C. Identification of the mycothiol synthase gene (mshD) encoding the acetyltransferase producing mycothiol in actinomycetes. Arch. Microbiol. 178 (2002) 331–337. [DOI] [PMID: 12375100]
3.  Vetting, M.W., Roderick, S.L., Yu, M. and Blanchard, J.S. Crystal structure of mycothiol synthase (Rv0819) from Mycobacterium tuberculosis shows structural homology to the GNAT family of N-acetyltransferases. Protein Sci. 12 (2003) 1954–1959. [DOI] [PMID: 12930994]
[EC 2.3.1.189 created 2010]
 
 
EC 2.4.1.250     
Accepted name: D-inositol-3-phosphate glycosyltransferase
Reaction: UDP-N-acetyl-α-D-glucosamine + 1D-myo-inositol 3-phosphate = 1-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-1D-myo-inositol 3-phosphate + UDP
For diagram of mycothiol biosynthesis, click here
Glossary: mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy-α-D-glucopyranosyl]-1D-myo-inositol
Other name(s): mycothiol glycosyltransferases; MshA; UDP-N-acetyl-D-glucosamine:1D-myo-inositol 3-phosphate α-D-glycosyltransferase
Systematic name: UDP-N-acetyl-α-D-glucosamine:1D-myo-inositol 3-phosphate α-D-glycosyltransferase (configuration-retaining)
Comments: The enzyme, which belongs to the GT-B fold superfamily, catalyses the first dedicated reaction in the biosynthesis of mycothiol [1]. The substrate was initially believed to be inositol, but eventually shown to be D-myo-inositol 3-phosphate [2]. A substantial conformational change occurs upon UDP binding, which generates the binding site for D-myo-inositol 3-phosphate [3].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Newton, G.L., Koledin, T., Gorovitz, B., Rawat, M., Fahey, R.C. and Av-Gay, Y. The glycosyltransferase gene encoding the enzyme catalyzing the first step of mycothiol biosynthesis (mshA). J. Bacteriol. 185 (2003) 3476–3479. [DOI] [PMID: 12754249]
2.  Newton, G.L., Ta, P., Bzymek, K.P. and Fahey, R.C. Biochemistry of the initial steps of mycothiol biosynthesis. J. Biol. Chem. 281 (2006) 33910–33920. [DOI] [PMID: 16940050]
3.  Vetting, M.W., Frantom, P.A. and Blanchard, J.S. Structural and enzymatic analysis of MshA from Corynebacterium glutamicum: substrate-assisted catalysis. J. Biol. Chem. 283 (2008) 15834–15844. [DOI] [PMID: 18390549]
[EC 2.4.1.250 created 2010]
 
 
EC 2.8.4.2     
Accepted name: arsenate-mycothiol transferase
Reaction: arsenate + mycothiol = arseno-mycothiol + H2O
Glossary: mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy--D-glucopyranosyl]-1D-myo-inositol
Other name(s): ArsC1; ArsC2; mycothiol:arsenate transferase
Systematic name: mycothiol:arsenate S-arsenotransferase
Comments: Reduction of arsenate is part of a defence mechanism of the cell against toxic arsenate. The product arseno-mycothiol is reduced by EC 1.20.4.3 (mycoredoxin) to arsenite and mycothiol-mycoredoxin disulfide. Finally, a second mycothiol recycles mycoredoxin and forms mycothione.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Ordonez, E., Van Belle, K., Roos, G., De Galan, S., Letek, M., Gil, J.A., Wyns, L., Mateos, L.M. and Messens, J. Arsenate reductase, mycothiol, and mycoredoxin concert thiol/disulfide exchange. J. Biol. Chem. 284 (2009) 15107–15116. [DOI] [PMID: 19286650]
[EC 2.8.4.2 created 2010]
 
 
EC 3.5.1.103     
Accepted name: N-acetyl-1-D-myo-inositol-2-amino-2-deoxy-α-D-glucopyranoside deacetylase
Reaction: 1-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-1D-myo-inositol + H2O = 1-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-1D-myo-inositol + acetate
For diagram of mycothiol biosynthesis, click here
Glossary: mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy-α-D-glucopyranosyl]-1D-myo-inositol
Other name(s): MshB
Systematic name: 1-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-1D-myo-inositol acetylhydrolase
Comments: This enzyme is considered the key enzyme and rate limiting step in the mycothiol biosynthesis pathway [1]. In addition to acetylase activity, the enzyme possesses weak activity of EC 3.5.1.115, mycothiol S-conjugate amidase, and shares sequence similarity with that enzyme [2]. The enzyme requires a divalent transition metal ion for activity, believed to be Zn2+ [3].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Rawat, M., Kovacevic, S., Billman-Jacobe, H. and Av-Gay, Y. Inactivation of mshB, a key gene in the mycothiol biosynthesis pathway in Mycobacterium smegmatis. Microbiology 149 (2003) 1341–1349. [DOI] [PMID: 12724395]
2.  Newton, G.L., Av-Gay, Y. and Fahey, R.C. N-Acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside deacetylase (MshB) is a key enzyme in mycothiol biosynthesis. J. Bacteriol. 182 (2000) 6958–6963. [DOI] [PMID: 11092856]
3.  Maynes, J.T., Garen, C., Cherney, M.M., Newton, G., Arad, D., Av-Gay, Y., Fahey, R.C. and James, M.N. The crystal structure of 1-D-myo-inosityl 2-acetamido-2-deoxy-α-D-glucopyranoside deacetylase (MshB) from Mycobacterium tuberculosis reveals a zinc hydrolase with a lactate dehydrogenase fold. J. Biol. Chem. 278 (2003) 47166–47170. [DOI] [PMID: 12958317]
[EC 3.5.1.103 created 2010]
 
 
EC 3.5.1.115     
Accepted name: mycothiol S-conjugate amidase
Reaction: a mycothiol S-conjugate + H2O = an N-acetyl L-cysteine-S-conjugate + 1-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-1D-myo-inositol
Glossary: mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy-α-D-glucopyranosyl]-1D-myo-inositol
N-acetyl L-cysteine-S-conjugate = mercapturic acid
Other name(s): MCA
Systematic name: mycothiol S-conjugate 1D-myo-inositol 2-amino-2-deoxy-α-D-glucopyranosyl-hydrolase
Comments: The enzyme that is found in actinomycetes is involved in the detoxification of oxidizing agents and electrophilic antibiotics. The enzyme has low activity with 1-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-1D-myo-inositol as substrate (cf. EC 3.5.1.103, N-acetyl-1-D-myo-inositol-2-amino-2-deoxy-α-D-glucopyranoside deacetylase) [2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Newton, G.L., Av-Gay, Y. and Fahey, R.C. A novel mycothiol-dependent detoxification pathway in mycobacteria involving mycothiol S-conjugate amidase. Biochemistry 39 (2000) 10739–10746. [DOI] [PMID: 10978158]
2.  Steffek, M., Newton, G.L., Av-Gay, Y. and Fahey, R.C. Characterization of Mycobacterium tuberculosis mycothiol S-conjugate amidase. Biochemistry 42 (2003) 12067–12076. [DOI] [PMID: 14556638]
[EC 3.5.1.115 created 2013]
 
 
EC 6.3.1.13     
Accepted name: L-cysteine:1D-myo-inositol 2-amino-2-deoxy-α-D-glucopyranoside ligase
Reaction: 1-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-1D-myo-inositol + L-cysteine + ATP = 1-O-[2-(L-cysteinamido)-2-deoxy-α-D-glucopyranosyl]-1D-myo-inositol + AMP + diphosphate
For diagram of mycothiol biosynthesis, click here
Glossary: mycothiol = 1-O-[2-(N2-acetyl-L-cysteinamido)-2-deoxy--D-glucopyranosyl]-1D-myo-inositol
Other name(s): MshC; MshC ligase; Cys:GlcN-Ins ligase; mycothiol ligase
Systematic name: L-cysteine:1-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-1D-myo-inositol ligase (AMP-forming)
Comments: This enzyme is a key enzyme in the biosynthesis of mycothiol, a small molecular weight thiol found in Mycobacteria spp. and other actinomycetes. Mycothiol plays a fundamental role in these organisms by helping to provide protection from the effects of reactive oxygen species and electrophiles, including many antibiotics. The enzyme may represent a novel target for new classes of antituberculars [2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Fan, F., Luxenburger, A., Painter, G.F. and Blanchard, J.S. Steady-state and pre-steady-state kinetic analysis of Mycobacterium smegmatis cysteine ligase (MshC). Biochemistry 46 (2007) 11421–11429. [DOI] [PMID: 17848100]
2.  Gutierrez-Lugo, M.T., Newton, G.L., Fahey, R.C. and Bewley, C.A. Cloning, expression and rapid purification of active recombinant mycothiol ligase as B1 immunoglobulin binding domain of streptococcal protein G, glutathione-S-transferase and maltose binding protein fusion proteins in Mycobacterium smegmatis. Protein Expr. Purif. 50 (2006) 128–136. [DOI] [PMID: 16908186]
3.  Tremblay, L.W., Fan, F., Vetting, M.W. and Blanchard, J.S. The 1.6 Å crystal structure of Mycobacterium smegmatis MshC: the penultimate enzyme in the mycothiol biosynthetic pathway. Biochemistry 47 (2008) 13326–13335. [DOI] [PMID: 19053270]
[EC 6.3.1.13 created 2009]
 
 


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