Abstract
The activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, a key enzyme of juvenile hormone biosynthesis, have been measured in the supernatants of homogenates (10,000 x g) prepared from the corpora allata of the adult tobacco hornworm moth, Manduca sexta. Enzyme activity was inhibited 80% by 50 mM NaF, a known phosphoprotein phosphatase inhibitor, if present during extirpation of the glands and all subsequent workup of the tissue. Reductase activity was also significantly decreased (20-30%) in homogenates preincubated with 4 mM MgCl2 and 2 mM ATP. These results provide evidence that reductase in the insect undergoes phosphorylation and dephosphorylation similar to that occurring with reductase of mammalian liver. If so, this would provide a rapid method for modulating juvenile hormone synthesis.
Highlights
From the *Departmentof Biochemistry, The University of Chicago, Chicago, Illinois 60637 a n d the IDepartment of Biochemistry, The University of Arizona, Tucson, Arizona 85724
Inactivation of the reductase is effected through phosmogenates (10,000 X g) prepared from the corpora al- phorylation by ATP catalyzed by a protein kinase
We reported that in CA homogenates, Mg-ATP and F- did not influence the activity of HMG-CoAreductase
Summary
Animals-Colonies of M. sexta were raised as previously described [15]. Eggs were generously provided by Dr J. HMG-CoA reductase activity was assayed by a modification of the this fact. EDTA (5 nm) had been routinely included in homogenization buffers for the measurement of HMG-CoA reductase. NaF, a known inhibitor of phosphoprotein phosphatases, was, included whenpreincubating homogenates with Mg-ATP to avoid this reactivation and to enhance the inhibition of reductase activity observed.
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