A comparison of the specificities of xanthine oxidase and aldehyde oxidase

摘要: Abstract This study directly compares the specificities of structurally similar hydroxylating enzymes, aldehyde oxidase and xanthine oxidase. Michaelis-Menten constants for a variety substrates were in general lower than those With respect to rates oxidation, basic similarity was preference compounds having substituted pyrimidine ring structure. Outstanding among differences effects number position substituents. Both enzymes readily oxidized unsubstituted C-monosubstituted heterocycles, but only C-disubstituted derivatives. Certain N-substitutions, however, enhanced substrate activity with oxidase, markedly decreased it Although both preferred oxo over amino substituents, there some specificity chemical nature Aldehyde not tolerated 6-substitution purine by alkyl, halogeno, cyano, or methylthio groups, while 6-hydroxyl 6-methylamino substituents The at which oxidation occurred influenced positions purines different site initially hydroxylated each enzyme.