[Method for the quantitative determination of penicillin acylase activity by the formation of phenylacetic acid]

The quantitative method for determination of penicillinacylase activity is described. The method is based on detection of phenylacetic acid (PAA) formed during hydrolysis of benzylpenicillin. PAA is extracted with toluol and nitrated with potassium nitrate solution in concentrated sulphuric acid followed by reduction of nitrophenylacetic acid into aminophenylacetic acid with zinc powder. Aminophenylacetic acid interacts with p-dimethylaminobenzaldehyde in acid medium forming a coloured compound (Schiff base). The optic density of the latter was determined with spectrophotometer SF-16 at 430 nm. The method was used for determination of acylase in Yersinia species and some other bacteria.