Isocaproaldehyde is reduced by NADPH + H+ to yield 4-methylpentan-1-ol and NADP+. This cytosolic reaction is catalyzed by AKR1B1 (aldose reductase). The purified human enzyme has been shown to catalyze this reaction efficiently in vitro; its abundance in adrenal tissue in humans and other mammals and its concordant expression with other enzymes of steroid hormone synthesis are consistent with it performing this role in vivo as well (Matsuura et al. 1996; Lefrancois-Martinez et al. 2004). The metabolic fate of 4-methylpentan-1-ol is unknown.