ECHS1 and hyperinsulinemic hypoglycemia, familial, 4: Taken together, it can be concluded from these results that in fibroblasts either a small amount of residual SCEH activity in patients is enough to maintain sufficient flux through the mitochondrial β-oxidation system since both expression of SCEH and its activity towards straight-chain fatty acyl-CoAs is high, or that another enzyme is additionally involved in fatty acid oxidation and can at least partially take over in case of an SCEH deficiency.