Reduced phytanic acid oxidase activity in cultured fibroblasts 2023-02-17T21:07:33Z Decreased phytanoyl-CoA hydroxylase activity PhyH activity low in fibroblasts Activity of the enzyme phytanoyl-CoA hydroxylase (PhyH; EC 1.14.11.18) below the lower limit of normal in cultured fibroblasts. PhyH plays a role in the catabolism of phytanic acid, a branched-chain fatty acid that is a normal constituent of the human diet. Abnormal enzyme activity in cultured fibroblasts