| Popis: |
Trihydroxyphenolic acids such as 3,4,5-trihydroxycinnamic acid (3,4,5-THCA) 4c and 2-(3,4,5-trihydroxyphenyl)acetic acid (3,4,5-THPA) 2c are strong antioxidants that are potentially useful as medicinal agents. Our results show that p-hydroxyphenylacetate (HPA) 3-hydroxylase (HPAH) from Acinetobacter baumannii can catalyze the syntheses of 3,4,5-THPA 2c and 3,4,5-THCA 4c from 4-HPA 2a and p-coumaric acid 4a, respectively. The wild-type HPAH can convert 4-HPA 2a completely into 3,4,5-THPA 2c within 100 min (total turnover number (TTN) of 100). However, the wild-type enzyme cannot efficiently synthesize 3,4,5-THCA 4c. To improve the efficiency, the oxygenase component of HPAH (C2) was rationally engineered in order to maximize the conversion of p-coumaric acid 4a to 3,4,5-THCA 4c. Results from site-directed mutagenesis studies showed that Y398S is significantly more effective than the wild-type enzyme for the synthesis of 3,4,5-THCA 4c; it can catalyze the complete bioconversion of p-coumaric acid 4a to 3,4,... |
