PEROXISOMAL ENZYMES IN THE HONEY-BEE MIDGUT

Citation
Dr. Jimenez et M. Gilliam, PEROXISOMAL ENZYMES IN THE HONEY-BEE MIDGUT, Archives of insect biochemistry and physiology, 31(1), 1996, pp. 87-103
Citations number
64
Categorie Soggetti
Entomology,Biology,Physiology
ISSN journal
07394462
Volume
31
Issue
1
Year of publication
1996
Pages
87 - 103
Database
ISI
SICI code
0739-4462(1996)31:1<87:PEITHM>2.0.ZU;2-3
Abstract
Peroxisomes are ubiquitous organelles that contain catalase (CAT) and an array of inducible enzymes that regulate aspects of lipid, purine, xenobiotic, eicosanoid, and phospholipid metabolism. Although peroxiso mes are recognized as essential components in the cellular economy of microorganisms, plants, and mammals, little is known about their speci alized functions in insect metabolism. Peroxisomal acyl-CoA oxidase (A CO) is a flavin-linked, H2O2-producing enzyme that regulates the beta- oxidation of long chain fatty acids. We measured ACO and CAT activity in midgut tissues from worker honey bees, Apis mellifera, of known age s from free-flying colonies. The ACO activity peaked in young worker b ees that digest and assimilate nutrients from pollen and from trophall axis. As the bees aged, ACO activity declined. Conversely, CAT activit y increased as the bees aged and reached its highest level in the olde st bees that were assayed. Isolated honey bee midguts were then fracti onated using sucrose and Metrizamide (MET) density gradient centrifuga tion. Organelle-bound CAT activity equilibrated in sucrose at densitie s between 1.19 and 1.22, which are typical of spherical 1 mu m peroxis omes. In the MET gradients, the organelle-bound CAT separated into two distinct fractions. The heavier fraction equilibrated at 1.21 and the lighter fraction at 1.15, a density commonly associated with microper oxisomes. These results support our ultrastructural and cytochemical d ata and suggest that the diverse functions of regionally specialized m idgut epithelial cells lead to a heterogeneous population of peroxisom al organelles. ACO activity confirms the role of midgut peroxisomes in the intermediary metabolism of lipids and the increasing CAT activity suggests that the midgut epithelium may metabolize deleterious pro-ox idants of aerobic metabolism associated with foraging and senescence. (C) 1996 Wiley-Liss, Inc.