The role of maslinic acid in the pentose phosphate pathway during growth of gilthead sea bream (Sparus Aurata)

NADPH produced in the pentose phosphate pathway (PPP) plays a central role in the reductive biosynthesis of membrane lipids, as well as in the maintenance of cell integrity; also, it has a key part in the synthesis of protein, the other member element. For that NADPH is involved in the growth processes. Our main objective is to study the effects of maslinic acid (MA) on kinetics and its molecular nature of NADPH-generating systems in the gilthead sea bream (S. aurata) as well as the possible changes of these enzymes related with several feeding conditions; for this, we have studied the kinetic and expression levels of glucose 6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), both PPP enzymes, in liver and white muscle. MA, a triterpene, stimulates growth, protein turnover rates and hyperplasia in fish. G6PDH and 6PGDH showed hyperbolic kinetics under all experimental conditions. With MA feeding, the specific activity, maximum velocity and catalytic efficiency of both enzymes increased in both tissue. The Michaelis constant changed with MA and fixed diet, and these changes being in relation to the substrate affinity. Moreover, we found that MA increased the protein levels studied, and this behaviour being consistent with the regulation of the number of enzyme molecules. These results show that G6PDH and 6PGDH are two inducible enzymes regulated by MA. Our findings corroborate that MA affect to the activity and expression of G6PDH and 6PGDH, confirming its role as markers of growth.