Enzymology of plasma membranes of insect intestinal cells

Abstract

The enzymology of insect intestinal cell plasma membranes is a field of scientific research that is in the earliest stages of development. In this paper the few published studies specifically designed to isolate plasma membranes from insect intestinal cells and determine the enzymes associated with them are reviewed in light of both older studies that approached these problems less directly and recent results from our laboratory.In the past few years reliable methods have been developed for the isolation of specific portions of plasma membranes from the epithelial cells of the midguts of a few insect larvae. These membrane preparations have been assayed for a variety of enzyme activities. Alkaline phosphatase, leucine aminopeptidase and γ-glutamyl transpeptidase have shown promise as potential markers for the plasma membranes of insect larval midgut cells. However, only the latter enzyme currently stands unchallenged as a marker for the apical portion of the plasma membrane of insect midgut columnar epithelial cells. No enzymes can yet be considered to be even tentatively established as markers for the basal or lateral portions of insect intestinal cells. © 1984 by the American Society of Zoologists.