AMACR (alpha-methylacyl-CoA racemase) catalyzes the stereoisomeric interconversion of (R)- and (S)-forms of alpha-methyl-branched-chain fatty acyl-CoA esters 1, serving as a key enzyme in branched-chain fatty acid metabolism. The enzyme acts exclusively on coenzyme A thioesters, accepting diverse substrates including pristanoyl-CoA, trihydroxycoprostanoyl-CoA (bile acid synthesis intermediate), and anti-inflammatory drugs like ibuprofen, but excludes 3-methyl-branched or linear-chain acyl-CoAs 1. AMACR localizes to peroxisomes, peroxisomal matrix, mitochondria, and cytosol, participating in fatty acid beta-oxidation and bile acid biosynthesis 2. Clinically, AMACR deficiency represents a peroxisomal disorder causing leukodystrophy and syndromic retinitis pigmentosa with retinal degeneration 32. AMACR is overexpressed in prostate and other cancers, serving as diagnostic marker P504S for urothelial carcinoma in situ 4. Recent evidence links AMACR to intestinal mucosal homeostasis, with decreased expression in ulcerative colitis patients correlating with mitochondrial dysfunction 5. AMACR expression patterns and genetic polymorphisms associate with prostate cancer risk, particularly in relation to branched-chain fatty acid metabolism 67. AMACR inhibitors show potential as novel cancer therapeutics, particularly for castrate-resistant prostate cancers 1.