This enzyme condenses acetyl-CoA with acetoacetyl-CoA to form HMG-CoA, which is the substrate for HMG-CoA reductase. HMGCS1 (3-Hydroxy-3-Methylglutaryl-CoA Synthase 1) is a Protein Coding gene. Among its related pathways are Terpenoid backbone biosynthesis and Metabolism. GO annotations related to HMGCS1 include protein homodimerization activity and isomerase activity. An important paralog of HMGCS1e is HMGCS2.