High-level expression of Bacillus subtilis hemA gene in Escherichia coli and the effect on the 5-ALA biosynthesis pathway
谷氨酰t-RNA还原酶基因（hemA）的高效表达

Bacillus subtilis glutamyl-tRNA reductase encoded by hemA gene, which is the rate-limitation enzyme in biosynthesis of 5-ALA. 5-ALA is the precursor of the biosynthesis of terapyrroles as well as an important functional molecular in medical and agricultural application. The hemA gene was polymerase chain reaction amplified from B. subtilis genome DNA and cloned into the expression vector pET28a. The hemA gene was High-level expressed in Escherichia coli BL21 (DE3) when induced by IPTG, in which the recombinant protein makes up 20% of total soluble protein through SDS-PAGE analysis. We also obtained the purified protein of HemA through the Ni2 -NAT affinity chromatography resin. Biosynthesis level of 5-ALA was enhanced responding to expression of the recombinant protein. The production of 5-ALA reached 40.2mg/L. The catabolite metabolism of 5-ALA porphyrins was also accelerated.