6a-hydroxylase

Pterocarpan 6a-hydroxylase (3,9-dihydroxypterocarpan 6a-hydroxylase) P6aH (DH6aH) 1.14.13.28 CytP450 (CYP93A) 202... 

Schopfer, C.R. et al., Molecular characterization and functional expression of dihydroxypterocar-pan 6a-hydroxylase, an enzyme specific for pterocarpanoid phytoalexin biosynthesis in soybean... 

Kochs, G., Werck-Reichhart, D., and Grisebach, H., Further characterization of cytochrome P450 involved in phytoalexin synthesis in soybean cytochrome P450 cinnamate 4-hydroxylase and 3,9-dihydroxyptero-carpan 6a-hydroxylase, Arch. Biochem. Biophys., 293, 187-194, 1992. 

Scheme 1.1 Pathway for the biosynthesis of the major classes of flavonoids. 1, Chalcone synthase 2, chalcone isomerase 3, flavone synthase 4, flavanone 3-hydroxylase 5, flavonol synthase 6, dihydroflavonol reductase 7, anthocyanidin synthase 8, anthocyanidin glucosyltransferase 9, chalcone-ketide reductase 10, chalcone isomerase 11, isoflavone synthase 12, isoflavone 2 -hydroxylase 13, isoflavone reductase 14, pterocarpan synthase 15, pterocarpan 6a-hydroxylase 16, prenyltransferase 17, prenylcyclase.

HAGMANN, M.-L., HELLER, W., GRISEBACH, H Induction of phytoalexin synthesis in soybean. Stereospecific 3,9-dihydroxypterocarpan 6a-hydroxylase from elicitor-induced soybean cell cultures. Eur. J.Biochem., 1984,142,127-131. 

KOCHS, G., GRISEBACH, H., Phytoalexin synthesis in soybean purification and reconstitution of cytochrome P450 3,9-dihydroxypterocarpan 6a-hydroxylase and separation from cytochrome P450 cinnamate 4-hydroxylase. Arch Biochem. Biophys., 1989,273,543-553. 

Bahadur N, Leathart JBS, Mutch E et al. (2002) CYP2C8 polymorphisms in Caucasians and their relationship with pacli-taxel 6a-hydroxylase activity in human livermicrosomes. Biochem Pharmacol 64 1579-1589 Dai D, Zeldin DC, Blaisdell JA et al. (2001) Polymorphisms in CYP2C8 decrease metabolism of the anticancer drug paclitaxel and arachidonic acid. Pharmacogenetics 11 597-607... 

An uncertainty also exists with human hepatic 6a-hydroxylase. Hyodeoxycholate has not been isolated from human bile. Despite the above-reported conversion of taurolithocholate to taurohyodeoxycholate [112], investigators have been unable to demonstrate hydroxylation of conjugated or free mono- or dihydroxy bile acids with... 

In patients treated with phenobarbital, tetrahydroxy bile acids become major urinary bile acids the ratio of the lj8,3a,7a,12a-tetrol to the 3a,6.a,7a,12a-tetrol was about 4 1. Stimulation of 6a-hydroxylase was evident from the presence of hyocholate in urine and plasma after 1.5-4.5 weeks on phenobarbital. Thus, phenobarbital stimulates 1/8- and 6a-hydroxylation [197]. 

Bahadur, N., J.B. Leathart, E. Mutch, D. Steimel-Crespi, S.A. Dunn, R. Gilissen et al. (2002). CYP2C8 polymorphisms in Caucasians and their relationship with paclitaxel 6a-hydroxylase activity in human liver microsomes. Biochem. Pharmacol. 64, 1579-1589. 

An additional enzyme, 6a-hydroxylase, is responsible for the formation of many pterocarpan derivatives (Barz and Welle, 1992 Heller and Forkmann, 1988). 6a-Hydroxypter-ocarpans [such as (-)-pisatin (101) and 6a,lla-dehydropt-erocarpan derivatives are well-known antifungal compounds (see the section on phytoalexins, below). 

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