Biochemical properties of amylase isozymes from Gammarus palustris. A comparative study

Two major alpha-amylase isozymes from Gammarus palustris were purified and characterized. These isozymes, Amy IW and Amy Ic, exhibit a seasonal pattern of expression. In this article we investigate whether the seasonal variation has an adaptive significance. In addition, the species-specific properties of amylases were studied. Purification of the isozymes was achieved by sequential glycogen-ethanol precipitation, Sephadex G-200 and ion exchange chromatography. Characterization in terms of Km, activity patterns at different temperatures, pH values and salt concentrations was done for both isozymes. In addition, the distribution of enzymatic products was analyzed in a high-performance liquid chromatography system. In all conditions tested, the two isozymes gave similar results. This observation suggests that the seasonal change in amylase expression pattern does not result in enzymes differentially suited for seasonal variation in conditions. A comparative analysis showed that G. palustris amylases are apparently distinct from other amylases. These distinctions were seen as an unusually low Km value, an activity peak at low NaCl concentration, a relatively high pH optimum and the predominant formation of maltotriose.