Inhibition of dimeric dihydrodiol dehydrogenase by 4-hydroxyphenylketone derivatives: aspects of inhibitor structure and binding specificity.
Dimeric dihydrodiol dehydrogenases from pig liver, monkey kidney, and rabbit lens were inhibited more potently by 4-hydroxyphenylketones such as 4-hydroxybenzaldehyde, 4-hydroxyphenylglyoxal, and 4-hydroxyacetophenone than by isoascorbate and ascorbate, known inhibitors of the enzymes. No significant inhibition was observed with 2- or 3-hydroxyphenylketones, phenylketones with a functional group other than a hydroxy group at the 4-position, and 4-hydroxyphenyl derivatives without a carbonyl group. The steady-state kinetic analyses of the inhibition of the pig liver enzyme indicated that the 4-hydroxyphenylketones, similarly to ascorbate and its epimer, bound to an enzyme-NADP+ binary complex as competitive inhibitors with respect to dihydrodiol substrate. The inhibition by the 4-hydroxyphenylketones was uncompetitive with respect to isoascorbate, and the addition of one of the 4-hydroxyphenylketones or isoascorbate with NADP+ afforded a great protective effect against inactivation of the enzyme by diethylpyrocarbonate or by heat treatment, which indicates that 4-hydroxyphenylketones and isoascorbate bind at the same site in or near the active center of the enzyme. The structural comparison of 4-hydroxybenzaldehyde and ascorbate suggests that the hydroxy group at C-5, carbonyl group at C-1 and lactone ring of ascorbate are important for the binding to the enzyme.
Shinoda
M
M
Gihoku General Hospital, Gifu.
Hara
A
A
Nakayama
T
T
Deyashiki
Y
Y
Yamaguchi
S
S
D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors*; D000818:Animals; D001665:Binding Sites; D000882:Haplorhini; D007659:Ketones / Q000494:pharmacology*; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D007908:Lens, Crystalline / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D046911:Macromolecular Substances; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010636:Phenols / Q000494:pharmacology*; D011817:Rabbits; D013329:Structure-Activity Relationship; D013552:Swine
D007659:Ketones; D046911:Macromolecular Substances; D010636:Phenols; D010088:Oxidoreductases; D000429:Alcohol Oxidoreductases; C023125:dihydrodiol dehydrogenases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C116788:cis-1,2-dihydro-1,2-dihydroxynaphthalene dehydrogenase