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3 Folia Biologica

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Partial characterization of a lipase from gypsy moth (Lymantria dispar L.) larval midgut

100%

Mrdakovic M. , Lazarevic J. , Peric_Mataruga V. , Ilijin L. , Vlahovic M.

nr 1-2

103-110

Lipase activity of the gypsy moth (Lymantria dispar L.) was studied by the spectrophotometric method using crude homogenate of fifth-instar larval midgut tissues as the enzyme source and p-nitrophenyl caprylate (pNPC) as substrate. A Km value of 0.310mM and a Vmax value of 1.479U/mg prot. were obtained for this substrate. Among various p-nitrophenyl esters tested, maximum activity was obtained for p-nitrophenyl caprylate and p-nitrophenyl caprate. The enzyme was most active at alkaline pH, with maximum at pH 8.2. Decreased activity was detected after preincubation in buffers of pH below 7.0 and above 8.2. The enzyme was unstable at room temperature. The enzyme was Ca2+ independent. Its activity was inhibited by PMSF, Fe2+, Ag+ and Pb2+, while Fe3+ inhibited enzyme activity by about 40%.

Effects of rearing density on larval growth and activity of digestive enzymes in Lymantria dispar L. (Lepidoptera: Lymantriidae)

100%

Lazarevic J. , Peric-Mataruga V. , Vlahovic M. , Mrdakovic M. , Cvetanovic D.

tom 52

nr 1-2

105-112

Density dependent responses of 4th, 5th and 6th instar gypsy moth larvae were studied at the level of larval mass, midgut loading and activities of three digestive enzymes (alpha-amylase, trypsin and leucine aminopeptidase). High density significantly reduced larval mass while midgut loading (expressed as relative midgut mass) did not change except in the 5th instar where it was increased at high density. Specific amylase and leucine aminopeptidase activities were not affected by crowding. Specific trypsin activity was on average higher in crowded than in isolated larvae. High density also affected the correlations between midgut protein content and activities of two proteolytic enzymes suggesting differences in regulatory mechanisms of insect digestion. The importance of these changes for survival under stressful conditions is discussed.

Changes in midgut and brain proteins in Morimus funereus larvae depending on nutritive substrate

72%

Ilijin L. , Jankovic-Tomanic M. , Mitic M. , Vlahovic M. , Lazarevic M. , Lazarevic J. , Peric-Mataruga V. , Prolic Z. , Nenadovic V.

Folia Biologica

2003

tom 51

nr 3-4

207-211

The response of Morimus funereus larvae to total starvation and refeeding with qualitatively different nutritive substrates (artificial diets supplemented with yeast as a source of B complex vitamins or with a digestibility reducer-tannic acid) was examined in this paper. Refeeding resulted in a compensatory increase of larval growth. Feeding and refeeding with qualitatively different nutritive substrates affected both quality and quantity of midgut and brain proteins. The observed differences suggest the possible switching of enzyme isoforms in M. funereus midgut and changes in synthesis/secretion of neurohormones, depending on food presence and its nutritional value.