Journal of Oceanography, Vol. 64 (No. 3), pp. 367-372, 2008
Yumiko Obayashi1,2* and Satoru Suzuki1
1Center for Marine Environmental Studies, Ehime University, Matsuyama 790-8577, Japan
2Division of Natural Sciences, International Christian University, Mitaka, Tokyo 181-8585, Japan
(Received 21 February 2007; in revised form 26 November 2007; accepted 26 November 2007)
Abstract: In aquatic environments extracellular enzymes are bound to microbial cells or exist in a free and adsorbed state. Various filters have been used to fractionate these enzymatic activities, but enzymes may be readily adsorbed onto some materials, and such adsorption can induce errors in the estimation of enzymatic activity. In this study we examined three filters to determine the most suitable filter for fractionation when estimating proteolytic enzyme activity in seawater. We found that the polycarbonate Nuclepore membrane, widely used for size fractionation because of its pore-size accuracy, was the most favorable for this purpose, even though it adsorbed slightly more enzymes than the low-protein-binding polyethersulfone membrane. We also found that trypsin- and chymotrypsin-type enzymes were more easily adsorbed than aminopeptidases.