Amylase Activity and Stability at High and Low Temperature Depending on Calcium and Other Divalent Cations

Abstract

The extracellular amylase produced by Bacillus caldolyticus at 70 C has previously been characterized as a Ca-dependent enzyme (Grootegoed et al., 1973); Heinen and Lauwers, 1975). Furthermore it had been shown that the enzyme consists of subunits with a MW of less than 10.000, which could probably be defined as microenzymes (Schenk and Bjorksten, 1973) because they are enzymically active in the low temperature range. From the ultrafiltration experiments we had also concluded that the subunits associate to a higher MW form when Ca is added to the low MW fraction, and that it is this divalent cation which binds the subunits. All bacterial amylases from mesophilic producers have been found to need Ca for full activity, and many contain also Zn or other metals (Vallee et al., 1959). But in general the role of Ca seems not to be specific, so that it can be substituted by various other cations (Vallee et al., 1959, Smolka et al., 1971, Levitzki and Reuben, 1973). So for us there remained the question whether the effect of Ca on the amylase from B. caldolyticus would also be unspecific. For this reason we have studied the effect of various cations at different temperatures. From these experiments we could expect to get some insight into the structural properties of the enzyme.