Notably, P103L substitution in D-amino acid oxidase (DAAO, the peroxisomal enzyme responsible for the catabolism of neutral and basic D-AAs) [61], was identified in four female patients affected by GC (with drinking and smoking habits) as well as in one with small intestine cancer and one with colon cancer [62]. The gene discussed is DAO; the disease is malignant colon neoplasm.