Fructose-1,6-bisphosphatase in mantle of the sea mussel Mytilus galloprovincialis Lmk—I. Purification and ion requirements

Abstract

1. 1. The enzyme fructose-1,6-bisphosphatase was purified from the mantle of the sea mussel Mytilus galloprovincialis Lmk. The purified enzyme showed a single band in SDS-polyacrylamide gel electrophoresis. The mol. wt and subunit mol. wt of the enzyme were 105,000 and 27,000, respectively. 2. 2. Divalent cations are essential for the enzyme activity. In the absence of chelating agents, FBPase 1 exhibits hyperbolic kinetics with respect to Mn 2+, Zn 2+ and Mg 2+. The K m for Mg 2+ is lower than the physiological concentration of cation in the tissue, whereas its K m for Mn 2+ and Zn 2+ is greater than the respective in vivo concentrations. 3. 3. The joint action of Mg 2+ and Zn 2+ increases the affinity of the enzyme for the substrate Fru-1,6-P 2, though V max is reduced. 4. 4. Na + strongly inhibits the enzyme even at very low concentrations. K + has no effect whatsoever.