trifunctional protein deficiency pathway 2015-02-19T14:03:09Z PW:0001627 SMP:00545 Trifunctional protein deficiency is caused by alteration in the fatty acid beta degradation pathway. Specifically, mutations in the alpha and beta subunits of the mitochondrial enzyme that catalyzes the last three steps, have been linked to this inherited metabolic condition. pathway vpetri inborn error of lipid metabolism pathway