ACAD11 (acyl-CoA dehydrogenase family member 11) is an atypical acyl-CoA dehydrogenase that catalyzes fatty acid β-oxidation with unique dual enzymatic functions 1. Unlike conventional ACADs, ACAD11 contains both a kinase domain and an ACAD domain, enabling it to process 4-hydroxy fatty acids by first phosphorylating the 4-hydroxy position, then eliminating the phosphate to form conventional 2-enoyl-CoAs for β-oxidation 12. ACAD11 is localized to peroxisomes and preferentially metabolizes longer-chain 4-hydroxy fatty acids compared to its mitochondrial counterpart ACAD10 3. The enzyme shows maximal activity towards saturated docosanoyl-CoA (C22:0) and is highly expressed in the central nervous system, particularly in white matter, where it collaborates with ACAD9 to accommodate the full spectrum of long-chain fatty acid substrates 4. ACAD11 deficiency leads to accumulation of 4-hydroxy acids in plasma and metabolic dysfunction 1. In disease contexts, ACAD11 is regulated by p53 during glucose starvation to promote oxidative phosphorylation and cell survival 5, and its deubiquitination by USP38 contributes to diabetic cardiomyopathy through disrupted fatty acid oxidation 6. The enzyme represents a critical gatekeeper of mammalian 4-hydroxy acid catabolism with tissue-specific roles in metabolic homeostasis.