SUBSTRATE-SPECIFICITY OF AN AFLATOXIN-METABOLIZING ALDEHYDE REDUCTASE

The enzyme from rat liver that reduces aflatoxin B-1-dialdehyde exhibi ts a unique catalytic specificity distinct from that of other aldo-ket o reductases. This enzyme, designated AFAR, displays high activity tow ards dicarbonyl-containing compounds with ketone groups on adjacent ca rbon atoms; 9,10-phenanthrene-quinone, acenaphthenequinone and camphor quinone were found to be good substrates. Although AFAR can also reduc e aromatic and aliphatic aldehydes such as succinic semialdehyde, it i s inactive with glucose, galacotse and xylose. The enzyme also exhibit s low activity towards alpha,beta-unsaturated carbonyl-containing comp ounds. Determination of the apparent K-m reveals that AFAR has highest affinity for 9, 10-phenanthrenequinone and succinic semialdehyde, and low affinity of glyoxal and DL-glyceraldehyde.