Journal of Lipid Research, Vol. 10, 636-641, November 1969
Copyright © 1969 by Lipid Research, Inc.

Characterization of phospholipase B of Culex pipiens fatigans

R. Hanumantha Rao and D. Subrahmanyam

Biochemistry Division, National Institute of Communicable Diseases, Delhi, India

Phospholipase B has been found in the mosquito Culex pipiens fatigans, and some of its properties have been studied. The enzyme had a high optimum temperature (45°C) and broad alkaline pH optimum (8-9). It was inactive toward diacylphospholipids, and hydrolyzed lysolecithin at a higher rate than lysophosphatidyl ethanolamine. The enzyme was heat labile, but lysolecithin protected it against heat inactivation. Phosphatidyl ethanolamine, phosphatidyl choline, deoxycholate, Fe⁺⁺⁺, and Hg⁺⁺ inhibited the enzyme markedly.

The enzyme was present mainly in larvae; little enzyme activity was detected in pupae or adults. The total and specific activities were highest in IV instar (6 day) and I instar (1st day) larvae, respectively. It was localized in the microsomal fraction and was distributed mainly in the abdomen and thorax of the insect. The enzyme was present at much higher levels of activity in larvae of the mosquitoes Anopheles stephensi and Aedes aegypti.

Supplementary key words mosquito vectors • developmental stages • lysophospholipids • alkaline pH optimum • high optimum temperature • deoxycholate • diacylphospholipid inhibition • heat lability • lysolecithin protection • Anopheles stephensi • Aedes aegypti>

Submitted on April 7, 1969
Accepted on July 8, 1969

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