Estimates of leucine aminopeptidase activity in different marine and brackish environments

Aim: Leucine aminopeptidase (LAP), an enzyme involved in the decomposition of-natural peptides, was measured in: different marine and brackish ecosyst ems, together with some environmental and microbiological parameters. Methods and Results: The fluorogenic compound L-leucine-7-amido-4-methyl co umarin was specifically used for the determination of this in situ activity . The enzyme data obtained from this comparative study highlighted the stro ng spatial and temporal variability of the distribution of LAP in aquatic e cosystems, which was sometimes related to the course of environmental varia bles such as salinity and organic carbon content. Conclusions: LAP assay has proved to be a rapid method providing useful inf ormation on the microbial metabolic processes involved in the mineralizatio n of organic matter. Significance and Impact of the Study: The determination of the potential ra tes of extracellular enzyme activity is of great ecological importance to e xtend knowledge on the role played by bacteria in aquatic biogeochemical cy cles.