[Construction of gene library of Arthrobacter BT801 and isolation & expression of hydantoinase gene]

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.

[Cloning and expression of L-N-carbamoylase gene from Arthrobacter BT801 in Escherichia coli]

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.

[Studies on bioconversion conditions and stereoselectivity of Arthrobacter K1108 hydantoinase]

The bioconversion conditions of hydantoinase of Arthrobacter K1108 were studied. It was shown that the optimum temperature of the enzyme is 55 degrees C, and the optimum pH is 7.0. The enzyme can be activated by Co2+ and Fe2+, while inhibited by Ca2+. The optimal substrate of the hydantoinase is 5-benzylhydantoin, while 5-phenylhydantoin and 5-indolylmethylhydantoin cannot effectively digested, showing a high specificity on the substrates. An investigation on the hydantoinase stereoselectivity mechanism showed that the N-carbamoylamino acid hydrolase is stereoselective but the hydantoin hydrolase is not.

Factors associated with hepatitis B virus DNA breakthrough in patients receiving prolonged lamivudine therapy

Factors associated with hepatitis B virus (HBV) DNA breakthrough and the significance of YMDD variants without the presence of wild-type YMDD during prolonged lamivudine treatment are unknown. We studied the amino acid sequence of codon 552 (YMDD motif) and codon 528 by means of a line probe assay in 159 chronic HBV patients (median follow-up 29.6 months). Pretreatment HBV DNA levels and alanine transaminase (ALT) levels correlated inversely with the time to HBV DNA breakthrough with YMDD variants (r = -0.46, P =.001; r = -0.45, P =.001 respectively). Patients harboring YMDD variants 3 months before HBV DNA breakthroughs had higher HBV DNA breakthrough levels compared with those without YMDD variants 3 months before HBV DNA breakthroughs (18.9 x 10(6) vs. 5.4 x 10(6) copies/mL, P =.007). Patients with HBV DNA breakthroughs had higher percentages of YMDD variants without the presence of wild-type YMDD compared with patients without HBV DNA breakthrough (25.6% vs. 9%, P =.007 for single M552I variant; 20.9% vs. 8.1%, P =.026 for single M552V variant; 30.2% vs. 9.9%, P =.004 for M552I/M552V variants). Patients with HBV DNA levels of more than 10(3) copies/mL after 6 months of lamivudine therapy had a 63.2% chance of subsequently developing YMDD variants. HBeAg seroconversion occurred in 2 patients after the emergence of YMDD variants. Only one patient developed YMDD variant after HBeAg seroconversion. There was no increase in the rate of development of YMDD variants or L528M mutation in patients receiving lamivudine 25 mg daily or famciclovir 500 mg 3 times a day before being given lamivudine 100 mg daily.

Characteristics of recombinant human butyrylcholinesterase

AIM

To study the biochemical-pharmacological properties of the recombinant human butyrylcholinesterase (rhBChE) and thereby to size up the potential possibility of using it as a detoxifying agent in succinylcholine intoxication.

METHODS

CHO-dhfr cells were transfected with plasmids by electroporation. BChE activity was determined colorimetrically by 5, 5'-dithiobis-(2-nitrobenzoic acid) (DTNB) method. Antigenicity was estimated by enzyme-linked immunosorbent assay and Western blot.

RESULTS

The maximal expression amounted to 25.83 ng.h-1/10(6) cells. The rhBChE was highly similar to the native human BChE (nhBChE) in terms of its catalytic property, substrate affinity, inhibitor sensitivity, reactivation, stability, and immunoreactivity with anti-nhBChE antibodies. Mice challenged with 1.5 lethal dose of succinylcholine preincubated with rhBChE survived without any symptoms of intoxication.

CONCLUSION

The rhBChE and nhBChE exhibit similar biochemical-pharmacological features. It is of potential value in practical use.

[Serum lipids and apolipoproteins AI, B100, CI, CII, and CIII in 142 patients with coronary heart disease]

Serum triglycerides (TG), cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and apolipoproteins AI, B100, CI, CII and CIII were analyzed in 142 patients with coronary heart disease (CHD) and 64 age-matched healthy subjects in the Chengdu area. Significantly increased TG and decreased HDL-C were found in the CHD patients (P less than 0.001). Serum apo AI and CII were significantly decreased in the CHD patients compared with the normal subjects (P less than 0.01 or P less than 0.001). Serum apo B100 and CIII were slightly higher in the CHD group than in the normal group (P less than 0.001 or P less than 0.05). No significant differences were observed in apo CI levels in the CHD patients when compared with the normal subjects. The results were discussed.