Journal of Lipid Research, Vol 26, 977-981, Copyright © 1985 by Lipid Research, Inc.
Nature of the inhibitory effect of collagenase on phosphodiesterase activity
P Engfeldt, P Arner and J Ostman
The level of phosphodiesterase (PDE) activity is lower in collagenase-
isolated human fat cells than in adipose tissue fragments. The inhibition
is not species-specific since collagenase also inhibits PDE in rat adipose
tissue and bovine heart. In subcellular fractions from isolated fat cells,
the PDE activities were lowest in the plasma membrane-enriched fractions
and highest in the cytosolic fractions. This is opposite to PDE in
subcellular fractions obtained from adipose tissue fragments. In
dose-response experiments, collagenase inhibited particulate PDE to a much
larger extent than it inhibited soluble PDE. The extracellular activities
of PDE were completely eliminated by collagenase. Repeated washings or
reincubation of the isolated fat cells did not restore the PDE activity. A
purified collagenase with low specific protease activity reduced the PDE
activity in isolated fat cells to a lesser extent than did a collagenase
with high specific protease activities. Collagen and several protease
inhibitors were ineffective in preventing the reduction of PDE after
exposure to collagenase. It is concluded that nonspecific proteases in the
collagenase preparations used for fat cell isolation interact with
particulate and soluble PDE causing an irreversible inhibition of PDE
activity in isolated fat cells. Of the various forms of PDE, plasma
membrane-associated PDE seems most sensitive to collagenase.