Specificity of papaya lipase in esterification with respect to the chemical structure of substrates

Esterification, catalyzed by papaya (Carica papaya) lipase (CPL), was studi ed with various alcohols and carboxylic acids under competitive conditions. Acids studied were straight-chain saturates of different chain lengths, wi th octanoic acid as the reference. Alcohols chosen were aliphatic straight- chain, branched, secondary, tertiary, terpene, and aromatic alcohols of dif ferent chain lengths, using 1-hexanol as the reference. The initial reactio n rate increased with increasing chain length of the acid from C4:0 to C18: 0, followed by a slight decrease with C20:0. In the case of alcohols, an op timum chain length of 8 carbon atoms was obtained for the straight-chain al iphatic group (C2 to C16). Ethanol, 1-propanol, and secondary and tertiary alcohols showed rather low reactivity. Branching of the alcohols was found not to affect the reactivity in esterification; among the terpenes, beta-ci tronellol [(2E)-3,7-dimethyl-6-octenol] and geraniol [(2E)-3,7-dimethylocta -2,6-dien-1-ol] were found to be more reactive than nerol [(2Z)-3,7-dimethy locta-2,6-dien-1-ol]. The highest reaction rate was found for the aromatic benzyl alcohol (phenylmethanol).