In contrast to amplification, 5-methylthioadenosine phosphorylase (MTAP) - an enzyme that contributes to methionine salvage from S-adenosylmethionine (SAM) - is frequently deleted in cancer patients due to its proximity to the tumour suppressor gene, cyclin dependent kinase inhibitor 2A (CDKN2A), on chromosome 9p2158,59. The gene discussed is CDKN2A; the disease is cancer.