The 3-hydroxymethyl-3-methylglutaryl-CoA lyase-like protein 1 (HMGCLL1) is a 370 amino acid protein that belongs to the HMG-CoA lyase family and is involved in the catabolism of branched amino acids, such as leucine and isoleucine. The gene encoding HMGCLL1 maps to human chromosome 6, which contains around 1,200 genes within 170 million base pairs of sequence. Deletion of a portion of the q arm of chromosome 6 is associated with early onset intestinal cancer suggesting the presence of a cancer susceptibility locus. Porphyria cutanea tarda is associated with chromosome 6 through the HFE gene which, when mutated, predisposes an individual to developing this porphyria. Notably, the PARK2 gene, which is associated with Parkinson's disease, and the genes encoding the major histocompatiblity complex proteins, which are key molecular components of the immune system and determine predisposition to rheumatic diseases, are also located on chromosome 6.