The Enzyme Database

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EC 2.1.1.98     
Accepted name: diphthine synthase
Reaction: 3 S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-aminopropyl]-L-histidine-[translation elongation factor 2] = 3 S-adenosyl-L-homocysteine + diphthine-[translation elongation factor 2] (overall reaction)
(1a) S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-aminopropyl]-L-histidine-[translation elongation factor 2] = S-adenosyl-L-homocysteine + 2-[(3S)-3-carboxy-3-(methylamino)propyl]-L-histidine-[translation elongation factor 2]
(1b) S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-(methylamino)propyl]-L-histidine-[translation elongation factor 2] = S-adenosyl-L-homocysteine + 2-[(3S)-3-carboxy-3-(dimethylamino)propyl]-L-histidine-[translation elongation factor 2]
(1c) S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-(dimethylamino)propyl]-L-histidine-[translation elongation factor 2] = S-adenosyl-L-homocysteine + diphthine-[translation elongation factor 2]
For diagram of diphthamide biosynthesis, click here
Glossary: diphthine = 2-[(3S)-3-carboxy-3-(trimethylamino)propyl]-L-histidine
Other name(s): S-adenosyl-L-methionine:elongation factor 2 methyltransferase (ambiguous); diphthine methyltransferase (ambiguous); S-adenosyl-L-methionine:2-(3-carboxy-3-aminopropyl)-L-histidine-[translation elongation factor 2] methyltransferase; Dph5 (ambiguous)
Systematic name: S-adenosyl-L-methionine:2-[(3S)-3-carboxy-3-aminopropyl]-L-histidine-[translation elongation factor 2] methyltransferase (diphthine-[translation elongation factor 2]-forming)
Comments: This archaeal enzyme produces the trimethylated product diphthine, which is converted into diphthamide by EC 6.3.1.14, diphthine—ammonia ligase. Different from the eukaryotic enzyme, which produces diphthine methyl ester (cf. EC 2.1.1.314). In the archaeon Pyrococcus horikoshii the enzyme acts on His600 of elongation factor 2.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 114514-25-9
References:
1.  Zhu, X., Kim, J., Su, X. and Lin, H. Reconstitution of diphthine synthase activity in vitro. Biochemistry 49 (2010) 9649–9657. [DOI] [PMID: 20873788]
[EC 2.1.1.98 created 1990, modified 2013, modified 2015]
 
 
EC 2.1.1.314     
Accepted name: diphthine methyl ester synthase
Reaction: 4 S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-aminopropyl]-L-histidine-[translation elongation factor 2] = 4 S-adenosyl-L-homocysteine + diphthine methyl ester-[translation elongation factor 2]
For diagram of diphthamide biosynthesis, click here
Glossary: diphthine methyl ester = 2-[(3S)-4-methoxy-4-oxo-3-(trimethylammonio)butyl]-L-histidine
Other name(s): S-adenosyl-L-methionine:elongation factor 2 methyltransferase (ambiguous); diphthine methyltransferase (ambiguous); Dph5 (ambiguous)
Systematic name: S-adenosyl-L-methionine:2-[(3S)-3-carboxy-3-aminopropyl]-L-histidine-[translation elongation factor 2] methyltransferase (diphthine methyl ester-[translation elongation factor 2]-forming)
Comments: This eukaryotic enzyme is part of the biosynthetic pathway of diphthamide. Different from the archaeal enzyme, which performs only 3 methylations, producing diphthine (cf. EC 2.1.1.98). The relevant histidine of elongation factor 2 is His715 in mammals and His699 in yeast. The order of the 4 methylations is not known.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Chen, J.-Y.C. and Bodley, J.W. Biosynthesis of diphthamide in Saccharomyces cerevisiae. Partial purification and characterization of a specific S-adenosylmethionine:elongation factor 2 methyltransferase. J. Biol. Chem. 263 (1988) 11692–11696. [PMID: 3042777]
2.  Moehring, J.M. and Moehring, T.J. The post-translational trimethylation of diphthamide studied in vitro. J. Biol. Chem. 263 (1988) 3840–3844. [PMID: 3346227]
3.  Lin, Z., Su, X., Chen, W., Ci, B., Zhang, S. and Lin, H. Dph7 catalyzes a previously unknown demethylation step in diphthamide biosynthesis. J. Am. Chem. Soc. 136 (2014) 6179–6182. [DOI] [PMID: 24739148]
[EC 2.1.1.314 created 2015]
 
 
EC 3.1.1.97     
Accepted name: methylated diphthine methylhydrolase
Reaction: diphthine methyl ester-[translation elongation factor 2] + H2O = diphthine-[translation elongation factor 2] + methanol
For diagram of diphthamide biosynthesis, click here
Glossary: diphthine methyl ester = 2-[(3S)-3-carboxy methyl ester-3-(trimethylammonio)propyl]-L-histidine
diphthine = 2-[(3S)-3-carboxy-3-(trimethylammonio)propyl]-L-histidine
Other name(s): Dph7; diphthine methylesterase (incorrect)
Systematic name: diphthine methyl ester acylhydrolase
Comments: The protein is only present in eukaryotes.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Lin, Z., Su, X., Chen, W., Ci, B., Zhang, S. and Lin, H. Dph7 catalyzes a previously unknown demethylation step in diphthamide biosynthesis. J. Am. Chem. Soc. 136 (2014) 6179–6182. [DOI] [PMID: 24739148]
[EC 3.1.1.97 created 2014, modified 2015]
 
 


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