Characterization of Human Salivary Esterase in Enzymatic Hydrolysis of Phthalate Esters.

Abstract

Enzymatic hydrolysis of phthalate esters in human saliva was investigated to characterize salivary esterase in the formation of monoesters from their diesters. The monoesters formed were analyzed by GC/MS after incubation of phthalate diesters in the saliva. Hydrolytic activity in the supernatant obtained by centrifugation of the saliva at 1350 × g was equivalent to that in whole saliva, and the activity was inhibited by the addition of denaturing protein. The hydrolytic activity was dependent on the protein concentration in the supernatant. The optimum temperature and pH of the hydrolysis was 50°C and 8.2, respectively. In addition, the 80% acetone powder of the supernatant showed high substrate specificity for straight-chain alkyl group of phthalate diesters, especially the butyl group, whereas almost no specificity was seen for the 2-ethylhexyl and benzyl groups. These results indicate that not the oral flora but salivary esterase, such as lingual lipase, is involved in phthalate monoester formation from the diesters in human saliva, and do not act on the hydrolysis of monoester.