EC	1.3.1.117
Accepted name:	hydroxycinnamoyl-CoA reductase
Reaction:	(1) dihydro-4-coumaroyl-CoA + NADP+ = trans-4-coumaroyl-CoA + NADPH + H+ (2) dihydroferuloyl-CoA + NADP+ = trans-feruloyl-CoA + NADPH + H+
Glossary:	trans-4-coumaroyl-CoA = (E)-3-(4-hydroxyphenyl)prop-2-enoyl-CoA trans-feruloyl-CoA = (E)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enoyl-CoA dihydro-4-coumaroyl-CoA = 3-(4-hydroxyphenyl)propanoyl-CoA dihydroferuloyl-CoA = 3-(4-hydroxy-3-methoxyphenyl)propanoyl-CoA
Other name(s):	MdHCDBR; hydroxycinnamoyl-CoA double bond reductase
Systematic name:	dihydro-4-coumaroyl-CoA:NADP+ 2,3-oxidoreductase
Comments:	Isolated from Malus X domestica (apple). Involved in dihydrochalcone biosynthesis.
References:	1.  Ibdah, M., Berim, A., Martens, S., Valderrama, A.L.H., Palmieri, L., Lewinsohn, E. and Gang, D.R. Identification and cloning of an NADPH-dependant hydroxycinnamoyl-CoA double bond reductase involved in dihydrochalcone formation in Malus X domestica Borkh. Phytochemistry 107 (2014) 24-31. [PMID: 25152451]
[EC 1.3.1.117 created 2018]
EC	2.3.1.74
Accepted name:	chalcone synthase
Reaction:	3 malonyl-CoA + 4-coumaroyl-CoA = 4 CoA + naringenin chalcone + 3 CO2
Glossary:	phloretin = 3-(4-hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)propan-1-one
Other name(s):	naringenin-chalcone synthase; flavanone synthase; 6′-deoxychalcone synthase; chalcone synthetase; DOCS; CHS
Systematic name:	malonyl-CoA:4-coumaroyl-CoA malonyltransferase (cyclizing)
Comments:	The enzyme catalyses the first committed step in the biosynthesis of flavonoids. It can also act on dihydro-4-coumaroyl-CoA, forming phloretin.
References:	1.  Ayabe, S.-I., Udagawa, A. and Furuya, T. NAD(P)H-dependent 6′-deoxychalcone synthase activity in Glycyrrhiza echinata cells induced by yeast extract. Arch. Biochem. Biophys. 261 (1988) 458–462. [PMID: 3355160] 2.  Heller, W. and Hahlbrock, K. Highly purified "flavanone synthase" from parsley catalyzes the formation of naringenin chalcone. Arch. Biochem. Biophys. 200 (1980) 617–619. [PMID: 7436427] 3.  Yahyaa, M., Ali, S., Davidovich-Rikanati, R., Ibdah, M., Shachtier, A., Eyal, Y., Lewinsohn, E. and Ibdah, M. Characterization of three chalcone synthase-like genes from apple (Malus x domestica Borkh.). Phytochemistry 140 (2017) 125–133. [PMID: 28482241]
[EC 2.3.1.74 created 1984, modified 2018]
EC	2.4.1.357
Accepted name:	phlorizin synthase
Reaction:	UDP-α-D-glucose + phloretin = UDP + phlorizin
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.
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. [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. [PMID: 27316677]
[EC 2.4.1.357 created 2018]
EC	3.2.1.62
Accepted name:	glycosylceramidase
Reaction:	(1) a β-D-glucosyl-N-acylsphingosine + H2O = a ceramide + β-D-glucose (2) a β-D-galactosyl-N-acylsphingosine + H2O = a ceramide + β-D-galactose (3) a flavonoid-O-β-D-glucoside + H2O = a flavonoid + β-D-glucose
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; LPH (gene name); LCT (gene name); glycosyl-N-acylsphingosine glycohydrolase
Systematic name:	β-D-glucosyl-N-acylsphingosine glycohydrolase (configuration-retaining)
Comments:	The enzyme, found in the intestinal mucosa, hydrolyses β-D-glucosyl and β-D-galactosyl residues from a very broad range of substrates using a retaining mechanism. Characterized substrates include glucosyl- and galactosyl-ceramides [3], O3-, O4′ and O7-glucosylated flavonoids [6], and the 2′-O-glucosylated dihydrochalcone phlorizin [1]. The enzyme includes two glycosyl hydrolase domains, both belonging to the GH1 family. While one domain is responsible for the activity described here, the other catalyses the reaction of EC 3.2.1.108, lactase [4,5]. cf. EC 3.2.1.45, glucosylceramidase and EC 3.2.1.46, galactosylceramidase.
References:	1.  Malathi, P. and Crane, R.K. Phlorizin hydrolase: a β-glucosidase of hamster intestinal brush border membrane. Biochim. Biophys. Acta 173 (1969) 245–256. [PMID: 5774775] 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. [PMID: 5082068] 3.  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] 4.  Zecca, L., Mesonero, J.E., Stutz, A., Poiree, J.C., Giudicelli, J., Cursio, R., Gloor, S.M. and Semenza, G. Intestinal lactase-phlorizin hydrolase (LPH): the two catalytic sites; the role of the pancreas in pro-LPH maturation. FEBS Lett. 435 (1998) 225–228. [PMID: 9762914] 5.  Arribas, J.C., Herrero, A.G., Martin-Lomas, M., Canada, F.J., He, S. and Withers, S.G. Differential mechanism-based labeling and unequivocal activity assignment of the two active sites of intestinal lactase/phlorizin hydrolase. Eur. J. Biochem. 267 (2000) 6996–7005. [PMID: 11106409] 6.  Nemeth, K., Plumb, G.W., Berrin, J.G., Juge, N., Jacob, R., Naim, H.Y., Williamson, G., Swallow, D.M. and Kroon, P.A. Deglycosylation by small intestinal epithelial cell β-glucosidases is a critical step in the absorption and metabolism of dietary flavonoid glycosides in humans. Eur J Nutr 42 (2003) 29–42. [PMID: 12594539]
[EC 3.2.1.62 created 1972, modified 1976, modified 2022]
EC	3.7.1.4
Accepted name:	phloretin hydrolase
Reaction:	phloretin + H2O = phloretate + phloroglucinol
Glossary:	phloretin = 3-(4-hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)propan-1-one phloretate = 3-(4-hydroxyphenyl)propanoate phloroglucinol = benzene-1,3,5-triol
Other name(s):	ErPhy; lactase-phlorerin hydrolase; C-acylphenol hydrolase; 2′,4,4′,6′-tetrahydroxydehydrochalcone 1,3,5-trihydroxybenzenehydrolase (incorrect)
Systematic name:	phloretin acylhydrolase (phloroglucinol-forming)
Comments:	Also hydrolyses other C-acylated phenols related to phloretin. Isolated from the fungus Aspergillus niger and the bacteria Pantoea agglomerans and Eubacterium ramulus.
References:	1.  Chatterjee, A.K. and Gibbins, L.N. Metabolism of phloridzin by Erwinia herbicola: nature of the degradation products, and the purification and properties of phloretin hydrolase. J. Bacteriol. 100 (1969) 594–600. [PMID: 5354935] 2.  Minamikawa, T., Jayasankar, N.P., Bohm, B.A., Taylor, I.E. and Towers, G.H. An inducible hydrolase from Aspergillus niger, acting on carbon-carbon bonds, for phlorrhizin and other C-acylated phenols. Biochem. J. 116 (1970) 889–897. [PMID: 5441377] 3.  Schoefer, L., Braune, A. and Blaut, M. Cloning and expression of a phloretin hydrolase gene from Eubacterium ramulus and characterization of the recombinant enzyme. Appl. Environ. Microbiol. 70 (2004) 6131–6137. [PMID: 15466559]
[EC 3.7.1.4 created 1972, modified 2018]