Structural And Enzymatic Characterization Of Phloretin Hydrolase MPhIG

Plyloretin, a flavonoid compound, is an intermediate during the degradation of flavone apigenin and flavanone naringenin by intestinal bacteria. In addition, it widely exists in apples, pears and other fruits. Flaconoids have been considered to have a wide range of pharmacological activities include anti-cancer, anti-inflammatory, blood coagulation etc. Among these, phloretin appears to be an inhibitor of GLUT2, which can inhibit glucose absorption by the small intestine and renal reabsorption, then as the starvation agent against cancer cells. It also displays an antioxidant activity in peroxynitrite scavenging and slows down the process at which melanocytes produce melanin. Hence, it can be applied to mask, creams, serums and other skin care produces as raw materials.On this thesis, carbon-carbon hydrolase mPh1G from Mycobacterium abscessus 103 has also the activity to hydrolyse 2’4’6’-Trihydroxyacetophenone (MAPG) in the same as Phy from Eubacterium ramulus which is the first phloretin hydrolase studied in substrate specificity clearly. Here, we report the crystal structure of mPhlG at the resolution of 1.83A with two molecules in the asymmetric unit. Structural analysis coupled with computational docking, site-directed mutagenesis, and enzymatic activity analysis reveal that the enzyme activity pocket consist of residues His133, Glu164, His269, E273, which surround an ion and a water molecule. In addition, residues His 118, Tyr125, His217, Tyr232 are predicted to be hydrogen-bonded to the hydroxyl groups in the phenol ring.