ABSTRACT
A new trans-4-hydroxy-l-proline (trans-Hyp) producing Bacillus cereus HBL-AI, was isolated from the air, which was screened just using l-proline as carbon and energy sources. This strain exhibited 73·4% bioconversion rate from initial l-proline (3 g l-1 ) to trans-Hyp. By sequencing the genome of this bacterium, 6244 coding sequences were obtained. Genome annotation analysis and functional expression were used to identify the proline-4-hydroxylase (BP4H) in HBL-AI. This enzyme belonged to a family of 2-oxoglutarate-related dioxygenases, which required 2-oxoglutarate and O2 as co-substrates for the reaction. Homologous modelling indicated that the enzyme had two monomers and contained conserved motifs, which included a distorted 'jelly roll' ß strand core and the residues (HXDXnH and RXS). The engineering Escherichia coli 3 Δ W3110/pTrc99a-proba-bp4h was constructed using BP4H, which transformed glucose to trans-Hyp in one step with high concentration of 46·2 g l-1 . This strategy provides a green and efficient method for synthesis of trans-Hyp and thus has a great potential in industrial application.
Subject(s)
Bacillus cereus/enzymology , Genome, Bacterial/genetics , Hydroxyproline/biosynthesis , Prolyl Hydroxylases/metabolism , Bacillus cereus/genetics , Bacillus cereus/isolation & purification , Bacillus cereus/metabolism , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Escherichia coli/genetics , Escherichia coli/metabolism , Glucose/metabolism , Ketoglutaric Acids/metabolism , Molecular Sequence Annotation , Proline/metabolism , Prolyl Hydroxylases/geneticsABSTRACT
Auxiliary liver transplantation (ALT) for hepatitis B virus (HBV)-related liver cirrhosis previously showed poor results, because the native liver was a significant source of HBV recurrence and the graft could be rapidly destroyed by HBV infection in an immunosuppressive condition. Four patients with HBV-related liver cirrhosis were unable to undergo orthotopic liver transplantation because the only available grafts of left lobe were too small. Under entecavir-based anti-HBV treatment, they underwent ALT in which the recipient left liver was removed and the small left lobe graft was implanted in the corresponding space. The mean graft weight/recipient weight was 0.49% (range, 0.38%-0.55%). One year after transplantation, the graft sizes were increased to 273% and the remnant livers were decreased to 44%. Serum HBV DNA was persistently undetectable. Periodic graft biopsy showed no signs of tissue injury and negative immunostaining for hepatitis B surface antigen and hepatitis B core antigen. After a mean follow-up period of 21 months, all patients live well with normal graft function. Our study suggests that ALT for HBV-related liver cirrhosis is feasible under entecavir-based anti-HBV treatment. Successful application of small left livers in end-stage liver cirrhosis may significantly increase the pool of left liver grafts for adult patients.