The Enzyme Database

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EC 2.4.1.357     
Accepted name: phlorizin synthase
Reaction: UDP-α-D-glucose + phloretin = UDP + phlorizin
For diagram of phloretin biosynthesis, click here
Glossary: phloretin = 3-(4-hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)propan-1-one
phlorizin = 3-(4-hydroxyphenyl)-1-[2-(β-D-glucopyranosyloxy)-4,6-dihydroxyphenyl]propan-1-one
Other name(s): MdPGT1: P2’GT
Systematic name: UDP-α-D-glucose:phloretin 2′-O-D-glucosyltransferase
Comments: Isolated from Malus X domestica (apple). Phlorizin inhibits sodium-linked glucose transporters. It gives the characteristic flavour of apples and cider.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Jugdé, H., Nguy, D., Moller, I., Cooney, J.M. and Atkinson, R.G. Isolation and characterization of a novel glycosyltransferase that converts phloretin to phlorizin, a potent antioxidant in apple. FEBS J. 275 (2008) 3804–3814. [DOI] [PMID: 18573104]
2.  Yahyaa, M., Davidovich-Rikanati, R., Eyal, Y., Sheachter, A., Marzouk, S., Lewinsohn, E. and Ibdah, M. Identification and characterization of UDP-glucose:Phloretin 4′-O-glycosyltransferase from Malus x domestica Borkh. Phytochemistry 130 (2016) 47–55. [DOI] [PMID: 27316677]
[EC 2.4.1.357 created 2018]
 
 
EC 3.2.1.62     
Accepted name: glycosylceramidase
Reaction: a glycosyl-N-acylsphingosine + H2O = a ceramide + a sugar
For diagram of glycolipid biosynthesis, click here
Glossary: a ceramide = an N-acylsphingosine
Other name(s): phlorizin hydrolase; phloretin-glucosidase; glycosyl ceramide glycosylhydrolase; cerebrosidase; phloridzin β-glucosidase; lactase-phlorizin hydrolase; phloridzin glucosidase
Systematic name: glycosyl-N-acylsphingosine glycohydrolase
Comments: Broad specificity [cf. EC 3.2.1.45 (glucosylceramidase) and EC 3.2.1.46 (galactosylceramidase)]. Also hydrolyses phlorizin to phloretin and glucose. The intestinal enzyme is a complex that also catalyses the reaction of EC 3.2.1.108 lactase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9033-10-7
References:
1.  Leese, H.J. and Semenza, G. On the identity between the small intestinal enzymes phlorizin hydrolase and glycosylceramidase. J. Biol. Chem. 248 (1973) 8170–8173. [PMID: 4752949]
2.  Lorenz-Meyer, H., Blum, A.L., Haemmerli, H.P. and Semenza, G. A second enzyme defect in acquired lactase deficiency: lack of small-intestinal phlorizin-hydrolase. Eur. J. Clin. Invest. 2 (1972) 326–331. [DOI] [PMID: 5082068]
3.  Malathi, P. and Crane, R.K. Phlorizin hydrolase: a β-glucosidase of hamster intestinal brush border membrane. Biochim. Biophys. Acta 173 (1969) 245–256. [DOI] [PMID: 5774775]
[EC 3.2.1.62 created 1972, modified 1976]
 
 
EC 3.2.1.108     
Accepted name: lactase
Reaction: lactose + H2O = D-galactose + D-glucose
Glossary: lactose = β-D-galactopyranosyl-(1→4)-α-D-glucopyranose
Other name(s): lactase-phlorizin hydrolase
Systematic name: lactose galactohydrolase
Comments: The enzyme from intestinal mucosa is isolated as a complex that also catalyses the reaction of EC 3.2.1.62 glycosylceramidase. cf. EC 3.2.1.33 amylo-α-1,6-glucosidase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9031-11-2
References:
1.  Lorenz-Meyer, H., Blum, A.L., Haemmerli, H.P. and Semenza, G. A second enzyme defect in acquired lactase deficiency: lack of small-intestinal phlorizin-hydrolase. Eur. J. Clin. Invest. 2 (1972) 326–331. [DOI] [PMID: 5082068]
2.  Ramaswamay, S. and Radhakrishnan, A.N. Lactase-phlorizin hydrolase complex from monkey small intestine. Purification, properties and evidence for two catalytic sites. Biochim. Biophys. Acta 403 (1975) 446–455. [DOI] [PMID: 810166]
3.  Schlegel-Haueter, S., Hore, P., Kerry, K.R. and Semenza, G. The preparation of lactase and glucoamylase of rat small intestine. Biochim. Biophys. Acta 258 (1972) 506–519. [DOI] [PMID: 5010299]
4.  Skovbjerg, H., Norén, O., Sjöström, H., Danielsen, E.M. and Enevoldsen, B.S. Further characterization of intestinal lactase/phlorizin hydrolase. Biochim. Biophys. Acta 707 (1982) 89–97. [DOI] [PMID: 6814489]
5.  Skovbjerg, H., Sjöström, H. and Norén, O. Purification and characterization of amphiphilic lactase-phlorizin hydrolase from human small-intestine. Eur. J. Biochem. 114 (1981) 653–661. [DOI] [PMID: 6786877]
6.  Asp, N.G., Dahlqvist, A. and Koldovský, O. Human small-intestinal β-galactosidases. Separation and characterization of one lactase and one hetero β-galactosidase. Biochem. J. 114 (1969) 351–359. [PMID: 5822067]
[EC 3.2.1.108 created 1984]
 
 


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