STX1B and Parkinson disease: To provide more facts about amino acid metabolism genetic loci contributing to PD across different populations, we conducted a case-control study by examining the genotypic and allelic frequencies of ACMSD-TMEM163 rs6430538, MCCC1 rs12637471, and BCKDK-STX1B rs14235 in 599 Taiwanese PD patients and 598 control subjects.