FURTHER CHARACTERIZATION OF ALKALINE-PHOSPHATASE ISOZYMES IN THE SILKWORM MIDGUT - EFFECTS OF AMINO-ACIDS AND METAL-IONS AND COMPARISON OF SUGAR CHAINS

1. Properties of purified membrane bound (m-ALP) and soluble alkaline phosphatase (s-ALP) from the silkworm midgut were studied. 2. L-Cysteine strongly inhibited both ALP activities and L-histidine was inhibitory for s-ALP. However, no appreciable effect was discernible by other amino acids. 3. The m-ALP restored its activity to 80% by addition of Zn2+ after inactivation by EDTA. Mg2+ was the most efficient for the restoration of s-ALP activity, but the effect of Zn2+ on s-ALP was lower than that on m-ALP. 4. Serial lectin affinity chromatography suggested that the major m-ALP is the biantennary complex type without a fucose residue, whereas s-ALP contains the sugar chain of high-mannose type.