Cloning and expression of L-N-carbamoylase gene from Arthrobacter BT801 in Escherichia coli / 生物工程学报

Hydantoin-utility-enzyme is widely used in enzymic production of various amino acids. One of its component, carbamoylase, is responsible for the conversion of N-carbamylamino acids to corresponding amino acids, which is crucial for the stereoselectivity and rate limiting. To improve the production of the enzyme, an L-N-carbamoylase gene from Arthrobacter BT801, a hydantoinase producting strain being able to convert 5-benzylhydantoin to phenylalanine, was cloned into E. coli. The gene was highly expressed in E. coli M15 under control of T5 promoter. A protein band about 44kD was detected by SDS-PAGE in the recombinant cell lysate. The objective product, which is principally in soluble form, represented 40% of total cell protein. The N-carbamoylase specific activity of the recombinant M15/pQE60- hyuC is 53 times higher than that of Arthrobacter BT801. The total biotransformation activity increased 8.1 times when. M15/pQE60-hyuC was added into the Arthrobacter BT801 reaction system. The successful expression of the enzyme is significant for the application of the hydantoinase producing strain or the enzyme thereof.

Construction of gene library of Arthrobacter BT801 and isolation & expression of hydantoinase gene / 生物工程学报

Hydantoinase can be widely used in enzymic production of various amino acids. In order to obtain the hydantoinase genes in Arthrobacter BT801, its chromatosomal DNA is isolated and partialy digested with Sau3A I to collect fragments of about 30kb. Then, this fragment is inserted into the Hpa I and Pst I site of cosmid pKC505. The genomic library was thus constructed by packing in vitro with lambda phage package protein and transfecting E. coli DH5alpha. A positive transformant was selected from the library using thin layer chromatography and other methods. A DNA fragment containing complete hydantoinase genes was sequenced by sub-cloning into pUC18. The gene can express active protein under control of its own promoter and T5 promoter in E. coli. The isolation of the gene established foundition for research and application of the hydantoinase.