Dehydroepiandrosterone, a mammalian glucose-6-phosphate dehydrogenase inhibitor, prevented Avy/a mice from becoming obese. Decreased accumulation of triacylglycerol accounted for a large portion of the weight difference between treated and control Avy/a mice. Hepatic lipogenesis as measured by 3H2O incorporation into total lipid was less in the dehydroepiandrosterone-treated mice. Dehydroepiandrosterone did not suppress appetite and had no apparent toxic effects at the doses used, and its weight controlling effects were reversible upon withdrawal of treatment.

Several pituitary preparations from various species, including two purzed follicle-stimulating hormone preparations, inhibited the ~-glyceraldehyde-3-phosphate dehydrogenase reaction. The active factor in those preparations that caused the apparent inhibition has been identified as an enzyme, triose phosphate isomerase. Using ~-glyceraldehyde-3-phosphate as the substrate, the optimum pH for the isomerization reaction is 8.4. The partially purified enzyme has a specific activity of 34 pmol dihydroxyacetone phosphate isomerized x min-* x mg protein+. The Km of the enzyme for D-glyceraldehyde 3-phosphate is 0.79 mM, and the K m for dihydroxyacetone phosphate is 1.53 mM. Half of the enzyme activity is lost in 7 min at 55 "C. The molecular weight of the enzyme is estimated to be 56000. The electrophoretic mobility of the enzyme differs from tha.t of the muscle enzyme supplied by Sigma indicating a difference in amino acid composition between the two enzymes. Electrophoresis revealed the presence of two to three isozymes of the pituitary triose phosphate isomerase.Two preparations of follicle-stimulating hormone, supplied by The National Institute of Arthritis and Metabolic Disease, inhibited the reaction of D-glyceraldehyde-3-phosphate dehydrogenase using glyceraldehyde-3-phosphate as the substrate [l]. These two preparations were of ovine (lot #S-4) and porcine (lot # P-1) origin. Another ovine preparation (lot #S-7) did not inhibit this reaction [l]. We thus concluded that the inhibitor was not follicle-stimulating hormone but a contaminant [l]. We also concluded that the inhibitor was not one of the known pituitary hormones we had tested, since none of them inhibited the ~-glyceraldehyde-3-phosphate dehydrogenase reaction El].Bornstein and his associates have reported the isolation of a factor, InG, from a pH-2 hydrolyzate of ovine growth hormone that inhibited D-glyceraldehyde-3-phosphate dehydrogenase and possessed other biological properties [2,3]. The amino acid sequence at both the amino terminal and carboxyl terminal of InG suggested that InG was a peptide from growth hormone that consisted of residues 164 to 188 [4]. A peptide synthesized according to the proposed amino acid sequence of InG had all the biological activities of the isolated InG [a].

No abstract