MTAP expression is crucial for the catabolism of methylthioadenosine, which is a by-product of polyamine biosynthesis in the methionine salvage pathway. Protein expression is decreased by homozygous deletion and promoter hypermethylation.http://www.creative-enzymes.com/product/Smethyl5thioadenosine-Phosphorylase-From-Human-Recombinant_1440.html