Paul L. Guss

Esterases and the identification of lipases from eggs of Diabrotica undecimpunctata howardi and D. virgifera

Abstract Soluble esterases from eggs of Diabrotica undecimpunctata howardi and D. virgifera were examined by polyacrylamide gel electrophoresis. Eggs from D.undecimpunctata howardi exhibited from 10 to 16 electrophoreticallyseparable esterases depending on age; prediapause eggs from D. virgifera contained 6 or 7 esterases depending on whether α- or β-naphthol substrates were used. Zymograms of eggs of both species contained a single zone of activity that was inhibited by 5 × 10−5 M eserine. Organophosphorus compounds produced inhibitory effects depending on which compound was used. Two esterase bands from eggs of D. undecimpunctata howardi were identified as lipases by direct comparisons of estrolytic and lipolytic activities in eluates from gel sections. The lipases could not be distinguished from other esterases on polyacrylamide gel zymograms with α-naphthyl caprylate or longer-chain naphthol esters.

On the regulation of lipolysis in an insect egg. Observations in vitro.

Abstract The triglycerides of eggs of the western corn rootworm ( Diabrotica virgifera LeConte, Coleoptera: Chrysomelidae ) are unavailable to an apparently freely active triglyceride lipase (glycerol ester hydrolase, EC 3.1.1.3) in isotonic homogenates. Homogenization of the eggs in a hypotonic medium or treatment of isotonic homogenates with freeze-thaw or sonication will release the triglycerides permitting hydrolysis by endogenous lipase. The observations suggest that a case of structure-linked substrate latency has been observed.

Lipase from egg of southern corn rootworm

The lipolytic activity in homogenates and aqueous extracts of acetone powders of eggs of the southern corn rootworm (Diabrotica undecimpunctata howardi Barber) was studied. The general properties were determined using as substrate olive oil in an emulsion stabilized by gum arabic. Bovine serum albumin or Triton X-100 were required in the assay system; they protected the enzyme from spontaneous denaturation. The lipase had activity optima at pH 7 and at 45 C. The preparation was inactive towards triacetin, and activity increased in the series tripropionin<tributyrin<trihexanoin< trioctanoin<tridecanoin. Activity towards tridecanoin. Triolein was hydrolyzed to oleic acid and glycerol with no marked accumulation, even transient, of partial glycerides.