AMACR(Alpha-methylacyl-CoA racemase) belongs to the CaiB/BaiF CoA-transferase family. It is a mitochondrial and peroxisomal enzyme that catalyzes the conversion of 2R stereoisomers of phytanic and pristanic acid to their S counterparts. AMACR has previously been shown to be a highly sensitive marker for colorectal and clinically localized prostate cancer (PCa). However,AMACR expression is down-regulated at the transcript and protein level in hormone-refractory metastatic PCa,suggesting a hormone-dependent expression of AMACR. It has 3 isoforms produced by alternative splicing. Defects in AMACR are the cause of alpha-methylacyl-CoA racemase deficiency (AMACRD) and congenital bile acid synthesis defect type 4 (CBAS4).