We examined the possible implication of ras in the regulation of the activity of several metabolic enzymes by employing an inducible H-ras expression system (RFLSVrasLAP cell line), in which the addition of IPTG decreases the levels of ras p21 3-fold. We measured the activity of hexokinase (E.C. 2.7.1.1.), glucose phosphate isomerase (E.C. 5.3.1.9), phospho-fructokinase (E.C. 2.7.1.11), aldolase (E.C. 4.1.2.13), phosphoglycerate kinase (E.C. 2.7.2.3), enolase (E.C. 4.2.1.11), pyruvate kinase (E.C. 2.7.1.40), lactate dehydrogenase (E.C. 1.1.1.27), adenosine deaminase (E.C. 3.5.4.4) and purine nucleoside phosphorylase (E.C. 2.4.2.1) from cells grown in the presence and absence of IPTG. We found that the addition of IPTG to RFLSVrasLAP cells led to lower activity of phosphoglycerate kinase (p=0.004), enolase (p=0.027) and pyruvate kinase (p=0.031). Enolase mRNA levels were found to be increased in cells overexpressing either the normal or mutant H-ras. The total rate of glycolysis was not affected by H-ras expression indicating that the implication of H-ras in the activity of phosphoglycerate kinase, enolase and pyruvate kinase may be associated with glycolysis-independent functions of these enzymes. Adenosine deaminase activity was found to increase after IPTG addition (P=0.009), indicating also a possible role for H-ras in the control of the purine nucleotide salvage pathway.

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