ALKALINE-PHOSPHATASE ISOZYMES IN INSECTS AND COMPARISON WITH MAMMALIAN ENZYME

Studies of insect alkaline phosphatases (ALPs) are reviewed, including general insect isozyme papers from earlier periods, Results of bioche mical and genetic investigations of the silkworm midgut ALPs are descr ibed. The membrane-bound (m-ALP) and soluble form (s-ALP) are controll ed by distinct genes on the same chromosome, These isozymes were diffe rent in tissue localization, antigenicity, stability under alkaline co nditions and sugar chains. Compared with mammalian ALPs, silkworm ALPs represented specificity in the monomeric structure, tissue localizati on and inhibition by amino acids. The amino acid sequence deduced from cDNA sequence of silkworm m-ALP showed 42.7-44.6% homology to three h uman types of ALP. Comparison of the amino acid sequences in functiona lly important parts of various ALP isozymes showed a significant conse rvation. Physiological roles of ALPs were discussed and the significan ce of the study in temporal and spatial regulations of both silkworm A LP genes was pointed out, In addition, the evolutionary relationship a mong various enes was discussed.