The function of ACAA1 (acetyl-CoA acyltransferase 1, Ensembl gene identifier ENSG00000060971) is as follows. Responsible for the thiolytic cleavage of straight chain 3- keto fatty acyl-CoAs (3-oxoacyl-CoAs) (PubMed:11734571, PubMed:2882519). Plays an important role in fatty acid peroxisomal beta-oxidation (PubMed:11734571, PubMed:2882519). Catalyzes the cleavage of short, medium, long, and very long straight chain 3- oxoacyl-CoAs (PubMed:11734571, PubMed:2882519). May play a role in peroxisomal beta-oxidation step in polyunsaturated fatty acids (PUFAs) biosynthesis. Possibly regulates systemic levels of docosahexaenoic acid (DHA, C22:6n-3) through a process involving endoplasmic reticulum desaturation and elongation of alpha-linolenic acid (ALA, C18:3n-3) to form tetracosahexaenoic acid (THA, C24:6n-3), which is then beta- oxidized to DHA in peroxisomes. {ECO:0000303|PubMed:10903473, ECO:0000303|PubMed:35951481, ECO:0000303|PubMed:7685190, ECO:0000305|PubMed:11734571, ECO:0000305|PubMed:2882519, ECO:0000305|PubMed:35951481}.