No abstract

Substrate specificity of the acyltransferase activity of the lipase (EC 3.1.1.3) from Candida parapsilosis CBS 604 was studied in aqueous media. The specificity toward both acid and alcohol parts of a large number of acylglycerols and aliphatic esters was investigated. This lipase showed a high activity in the presence of esters with long-chain fatty acids and particularly unsaturated fatty acids with a cis-delta 9 double bond. It was observed that the activity profile depended not only on the alcohol part of the acyl ester, but also on the temperature of the reactant medium. The best lipid substrates had their melting point between -40 to +20 degrees C, 14 to 18 carbon atoms in the acyl group and 1 to 4 carbon atoms in the alkyl group. The enzyme, defined as an acyltransferase in a previous paper, showed a high affinity for primary and secondary alcohols with a short carbon chain (1 to 5 carbon atoms) as acyl acceptors. The influence of free alcohols in the reactant medium on the hydrolysis and alcoholysis activities of the enzyme is discussed. Two phenomena seem to be involved, depending on the alcohol: competition with water for the acyltransfer reaction and lipid substrate dilution when the alcohol places at the oil/water interface.

The lipase of Candida parapsilosis catalyses the formation of esters in aqueous media. In addition, the hydrolytic activity of the enzyme has been described in a recent publication as being selective for the 2 position, which is extremely rare. These features led to deeper investigation of the functioning and regioselectivity of the lipase in a biphasic aqueous medium. It is shown that, in addition to hydrolysis, the lipase of C. parapsilosis catalyses an alcoholysis reaction in the strict sense of the term, i.e. the transfer of fatty acyls groups from acylglycerols to various alcohols without direct involvement of water. In the presence of alcohol in the aqueous medium, alcoholysis occurred preferentially to hydrolysis. The enzyme thus displays transferase activity in which the acyl acceptor may be either water or alcohol. This activity is not stereospecific to either the acyl donor or acceptor. Hydrolysis and alcoholysis of monooleoylglycerols, dioleoylglycerols and trioleoylglycerols were studied successively. Investigation of the regiospecificity of alcoholysis in the presence of the lipase of C. parapsilosis showed that the selectivity of hydrolysis for the 2 position was, in fact, only apparent. In certain cases, and particularly when the initial substrate was a triacylglycerol, the similtaneous functioning of the two hydrolysis and alcoholysis reactions led to the appearance of equivalent quantities of 1,2(2,3)‐diacylglycerol and 1,3‐diacylglycerol in the reaction mixture; this proportion might then be interpreted as the result of selectivity of the hydrolysis reaction for position 2 of the triacylglycerol.

This study describes the influence of various factors on the hydrolysis and alcoholysis activities of the lipase from Candida parapsilosis (Ashford), Langeron and Talice in aqueous media. Optimal activities were obtained at 45°C and pH 6-6.5. The influence of the nature of the substrate on the temperature activity profiles was observed. Total or partial recovery of the activities was obtained when methanol was added to the enzyme extract after thermal denaturation. A tyrosin residue appeared to be necessary for lipase function. Magnesium was a required metal cofactor. These activities were optimal in the presence of high amounts of water (water activity > 0.9).JAOCS 72, 1367-1373 (1995).

The lipase of Candida parapsilosis catalyses the formation of esters in aqueous media. In addition, the hydrolytic activity of the enzyme has been described in a recent publication as being selective for the 2 position, which is extremely rare. These features led to deeper investigation of the functioning and regioselectivity of the lipase in a biphasic aqueous medium. It is shown that, in addition to hydrolysis, the lipase of C. parapsilosis catalyses an alcoholysis reaction in the strict sense of the term, i.e. the transfer of fatty acyls groups from acylglycerols to various alcohols without direct involvement of water. In the presence of alcohol in the aqueous medium, alcolysis occurred preferentially to hydrolysis. The enzyme thus displays transferase activity in which the acyl acceptor may be either water or alcohol. This activity is not stereospecific to either the acyl donor or acceptor. Hydrolysis and alcoholysis of monooleoylglycerols, dioleoylglycerols and trioleoylglycerols were studied successively. Investigation of the regiospecificity of alcoholysis in the presence of the lipase of C. parapsilosis showed that the selectivity of hydrolysis for the 2 position was, in fact, only apparent. In certain cases, and particularly when the initial substrate was a triacylglycerol, the similtaneous functioning of the two hydrolysis and alcoholysis reactions led to the appearance of equivalent quantities of 1,2(2,3)-diacylglycerol and 1,3-diacylglycerol in the reaction mixture; this proportion might then be interpreted as the result of selectivity of the hydrolysis reaction for position 2 of the triacylglycerol.