Modulation of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and malic enzyme activity by glucose and alanine in Atlantic salmon, Salmo salar L. hepatocytes
2003
Sanden, M. | Froyland, L. | Hemre, G.I.
The present study aims to elucidate interactions between glucose and alanine and their influence on pentose phosphate pathway (PPP) activity, using primary cultures of Atlantic salmon hepatocytes. Hepatocytes were exposed to either glucose or alanine for 24 h in different concentrations and combinations. High glucose concentration (10 mM) resulted in significant increased 6-phosphogluconate dehydrogenase (6PGDH) (EC1.1.1.44) and decreased malic enzyme (ME) (EC1.1.1.40) activities compared to physiological glucose concentrations (5 mM). Physiological alanine concentrations (5 mM) resulted in significant increased glucose-6-phosphate dehydrogenase (G6PDH) (EC1.1.1.49) enzyme activity compared to low alanine concentrations (0 mM). These results indicate that both glucose and alanine are able to modulate the oxidative part of the PPP in Atlantic salmon hepatocytes, and to inhibit cytosolic ME activity. This modulating effect of glucose and alanine adds to earlier suggestions of PPP being of major importance for the turnover of glucose in Atlantic salmon, and suggests a central role of alanine in the same pathway. However, no interaction between glucose and alanine was found.
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