SUPPRESSION OF RAT HEPATIC ALPHA-AMINO-BETA-CARBOXYMUCONATE-EPSILON-SEMIALDEHYDE DECARBOXYLASE (ACMSD) ACTIVITY BY LINOLEIC-ACID IN RELATION TO ITS INDUCTION BY GLUCOCORTICOIDS AND DIETARY-PROTEIN

Hepatic alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase [EC 4.1.1.45] (ACMSD), a key enzyme far tryptophan-niacin metabolism, is known to be suppressed by dietary polyunsaturated fatty acids. This enzyme is induced by glucocorticoid or dietary protein. We investigated the effect of linoleic acids on the induction of ACMSD activity by glucocorticoid at 40% or 10% casein levels and the effect of dietary linoleic acid on ACMSD activity in puromycin-treated rats to investigate the action of dietary linoleic acid. Dietary linoleic acid suppressed the hepatic ACMSD activity in the groups treated with and without glucocorticoid. However, in the case of the 10% casein diet, the ACMSD elevation ratio caused by glucocorticoid in the linoleic acid diet group was as large as that in the fat-free diet group. Puromycin suppressed ACMSD activity, but no additional suppression of hepatic ACMSD was observed by dietary linoleic acid.