申論題

3.Please translate the following paragraph into Chinese (25%)
 One of the main bottlenecks in the biosynthesis of natural products is limited enzyme activity. Integrating heterologous enzymes into microbial chassis may decrease their catalytic activities or even result in loss of function. Enhancing enzyme activity to accelerate production processes is a major goal in this area. Improving the catalytic activity of enzymes towards specific substrates through random mutagenesis is a typical strategy used in protein engincering. A yeast-active tyrosine hydroxylase was identified and randomly mutated by error-prone PCR to improve its catalytic activity by 4.3-fold. Further coexpression of L-3,4-dihydroxyphenylalanine (L-DOPA) decarboxylase and the engineered tyrosine hydroxylase enabled de novo dopamine production in yeast. Similarly, the catalytic activity of isopentenyl diphosphate isomerase (IDI) from Saccharomyces cerevisiae was enhanced by 2.53-fold through PCR-based random mutagenesis. The IDI with enhanced activity resulted in a 2.1-fold increase in lycopene titer (1.24 g/l) compared with the wild type. (Adapted from Trends in Biotechnology,2020)