ISSN:
0739-4462
Keywords:
enzyme
;
Diptera
;
sclerotization
;
Chemistry
;
Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
A specific alkaline phosphatase (ALPase) from the integument of white pupae has been purified 500-fold. The purification procedure included solubilization with Triton X-100, butanol extraction, fractionation with ammonium sulfate, and chromatography on concanavalin A-Sepharose, Sephadex G-200, and Sepharose 6B. Two peaks with enzyme activity were observed. The major peak had a molecular weight of approximately 180,000, while the minor peak, which had identical kinetic parameters and substrate specificity as those of the major one, was eluted in a high molecular weight form (about 900,000), probably cross-linked with chitin, since the enzyme was separated from the chitin only by lysozyme treatment. The enzyme hydrolyzes only tyrosine phosphate and β-glycerophosphate, with apparent Kms of 0.35 mM and 0.22 mM, respectively, but not serine phosphate, threonine phosphate, ATP, and AMP. The optimum pH was in the alkaline range, with a peak at pH 9.4. The divalent cations Mn2+, Mg2+, and Ba2+ had stimulatory actions, while Cu2+ exerted a very strong inhibitory action on the enzyme activity. The ALPase was inhibited by L-tyrosine in a dose-dependent fashion. At a concentration of 2 mM, L-tyrosine totally inhibited the enzyme activity, while L-phenylalanine inactivated the enzyme about 25%. The accumulated evidence that ALPase is involved in the sclerotization process of insect integument is discussed.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/arch.940110403
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