Determination of key enzyme activities in commercial peptidase and lipase preparations from microbial or animal sources

The enzyme complement of a selection of commercial food-grade peptidase and lipase preparations was investigated. Each preparation was assayed for protein content, proteinase activity at pH 5.5 and 7.0 at 37 °C using azocasein and semi-quantitatively assayed for lipase, peptidase, proteinase, phosphatase and glycosidase activity by the API-ZYM system. Each peptidase preparation was also assayed for various endo-, carboxy-, amino- and di-peptidase activities at pH 5.5 and 7.0 at 37 °C, using chromogenic or fluorogenic substrates, while each lipase preparation was assayed for esterase and lipase activity at pH 7.0 at 37 °C using p-nitrophenol substrates. All enzyme preparations were found to contain enzyme activities in addition to their stated main activity. According to the API-ZYM system the peptidase preparations contained varying levels of lipase, proteinase, peptidase, phosphatase and glycosidase activity, with the lipase preparations containing lipase, phosphatase and glycosidase activity. Only two peptidase and two lipase preparations contained significant amounts of proteinase activity as measured by azocasein. The peptidase and lipase activities of the preparations appeared to be dependent upon source. Most peptidase preparations had significantly more activity at pH 7.0 than at 5.5.