Acid Phosphatase Activity in the Digestive System of the Desert Locust Schistocerca Gregaria (Forskal)

Abstract

SummaryAcid phosphatase activity was determined biochemically in a homogenate of the digestive tract of the desert locust, S. gregaria. p-Nitrophenol was used as colorimetric standard and disodium p.nitrophenyl phosphate as substrate.The enzyme was found to have a linear relationship between concentration and activity, maximum activity at pH 4· 4, a Michaelis constant of 3·0 X 10-4M, and a temperature coefficient (QlO) of 2 ·10 between 20 and 30°C. Zero-order kinetics were maintained for 35 min at 40°C. Magnesium, calcium, and potassium ions and magnesium and phenylmercuric acetates slightly activated the enzyme, while ferrous ion, sodium fluoride, disodium hydrogen phosphate, and disodium hydrogen arsenate inhibited the enzyme. The magnesium ion concentration required for maximum activation was found to be O· 025M. INTRODUOTIONPhosphomonoesterases or phosphoric monoester hydrolases (3.l.3, Thompson 1962) are widely present in animal and plant tissues. During the last two decades work on biochemical characterization of phosphatases in insects has been done by Drilhon and Busnel (1945), Fitzgerald (1949), Rockstein and Herron (1951), Rockstein and Levine (1951), Denuce (1952), Rockstein (1956), Barker and Alexander (1958), Lambremont (1959), Fisk (1961, 1962), Hodgson (1963), Sridhara and Bhat (1963), Huddleston (1965), McCaman, Smith, andCock (1965), Raychaudri and Butz (1965), Hirano and Gilbert (1967), and Naqvi, Ashrafi, and Qadri (1967).In general these authors have studied the phosphomonoesterases in homogenates of holometabolous insects, whereas the present work deals with the biochemical characterization of acid phosphatase in the alimentary canal of a hemimetabolous insect, the desert locust, Schistocerca gregaria (Forskal). II. MATERIALS AND METHODS Enzyme SourceAdult locusts (28 days old) which had been fed on 6% glucose solution for 1 day prior to the experiment were selected as the source of enzymes. Locusts were dissected in cold doubledistilled demineralized water and the alimentary canal was transferred to a test tube containing 5 ml chilled double-distilled demineralized water. It was ground for exactly 3 min in a TeflonPyrex tissue grinder. The homogenate was filtered through a 2-mm layer of glass fibre in a

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“…Aldolase activity was assayed according to the method described by Ashrafi et al(1969). For the ALP analysis, a reaction mixture containing 50 µl of enzyme extract, 100 µl of substrate pnitrophenylphosphate (PNP) 1% in 0.1 M glycine/NaOH buffer pH 9, as well as the tested compounds were prepared in a micro plate of 96 wells and the final volumes were adjusted to 250 µl.…”