Identification of the characteristic amino-acid sequence for human alpha-amylase encoded by the AMY2B gene

Human salivary and pancreatic alpha-amylases (HSA and HPA) are the respective gene products of the AMY1 and AMY2A genes. AMY2B is a newly found human alpha-amylase gene. The presence of the AMY2B gene product (HXA) in the urine of healthy humans was examined. A mixture of alpha-amylases that seemed to contain HXA, judging from the substrate specificity, was purified from urine of healthy volunteers by affinity adsorption on starch and then by ion-exchange chromatography. The mixture was reduced and S-alkylated, and the product was digested with trypsin. The digest was separated by reversed-phase HPLC. LVGLLDLALEKDYVR and LVGLLDLALEK, which were found in the digest, are peptides of HXA, but not of HSA and HPA. The detection of these characteristic peptides of HXA demonstrates the presence of HXA in the urine of healthy humans.