[Seasonal variation of arylesterase activity and its consequence for enzymatic hydrolysis of phenylacetate].

Studies on red cell arylesterase activity were performed for two years by potentiometric titration using phenylacetate as substrate. From April to October enzymes had higher arylesterase activity than the rest of the year. During that period an increase of arylesterase activity by L-phyenyl-alanine had not been shown.