ABSTRACT
Immobilized whole-cells of Pichia pastoris harboring recombinant d-lactonase were entrapped in calcium alginate gels and used as an efficient biocatalyst for catalytic kinetic resolution of d,l-pantolactone. The immobilized whole-cell biocatalyst exhibited good catalytic stability, which was applied for stereospecific hydrolysis of d-pantolactone for up to 56 repeated batch reactions without obvious loss in the catalytic activity and enantioselectivity.
ABSTRACT
d-Pantolactone is a key chiral intermediate for the synthesis of d-pantothenic acid and its derivatives. Biocatalytic kinetic resolution of d,l-pantoyl lactone using d-lactonase is an efficient route to synthesize d-pantolactone. In this study, we report the expression of a novel d-lactonase TSDL in Escherichia coli host. The recombinant TSDL exhibited high hydrolysis activity and enantioselectivity toward d-pantolactone. The reaction conditions of the recombinant TSDL-catalyzed kinetic resolution of d,l-pantolactone was systematically investigated by whole cell biocatalysis. In addition, a preparative-scale reaction for bioproduction of d-pantoic acid was examined under optimized reaction conditions. This study presented an alternative enzymatic process for kinetic resolution of d,l-pantolactone.
ABSTRACT
OBJECTIVE: To investigate the effects of Xiehuo Bushen Decoction (XHBSD), a compound Chinese herbal medicine, on the survival and differentiation of transplanted neural stem cells (NSCs) in brains of rats with intracerebral hemorrhage, and to explore the mechanism of Xiehuo Bushen formula in promoting the survival of transplanted NSCs. METHODS: NSCs separated from hippocampuses of neonatal SD rats were cultured. Sixty-five panel reactive antibody (PRA) positive SD rats were selected by lymphocytotoxicity methods. The PRA positive rats were made into intracerebral hemorrhagic model and divided into three groups: cerebral hemorrhage group (n=15), NSCs transplanted group (n=25) and XHBSD group (n=25). XHBSD was orally administered after 5-bromodeoxyuridine (BrdU)-marked NSCs were transplanted in brains of rats with intracerebral hemorrhage in the XHBSD group. Rats in the other two groups were administered distilled water. The expressions of interferon gamma (IFN-gamma) and interleukin-4 (IL-4) mRNAs were measured by reverse transcription polymerase chain reaction (RT-PCR); the numbers of BrdU and 200 kD neurofilament (NF200) positive cells were detected by double-labeling immunofluorescence method. RESULTS: The expression of IFN-gamma mRNA was down-regulated significantly in the XHBSD group, but the expression of IL-4 mRNA was up-regulated significantly (P<0.05). The numbers of BrdU and NF200 positive cells were also increased remarkably in the XHBSD group. CONCLUSION: XHBSD can promote the survival and differentiation of transplanted NSCs, which may be related to inducing the expression of IL-4 mRNA and inhibiting the expression of IFN-gamma mRNA.
