ABSTRACT
A gene encoding NAD+-dependent sorbitol dehydrogenase (SDH) in peach fruit was cloned and expressed in Escherichia coli. Recombinant SDH protein with 6×His-tagged was localized exclusively in the cytoplasmic soluble fraction of E. coli when the strains were grown for 4-5 h at 37 ºC. Highly pure protein was isolated by Ni2+-resin chromatography with 150 mM imidazole in 50 mM Tris, pH 8.0, by elution. In order to ensure that the recombinant SDH could be used for further study, the fluorescence and ultraviolet spectrum of the recombinant SDH were detected. Recombinant SDH was confirmed to be capable of oxidizing sorbitol by enzymatic activity assay. The activity of the recombinant SDH was 2.73 U mg-1min-1, which was similar with that directly extracted from peach fruits. The activities of SDH extracted from the fruits in different periods (30, 60, 90 days after flowing) were 7.75, 5.95, 3.26 U mg-1min-1, respectively.
ABSTRACT
Background Some aboard studies showed that polyatomic pathway play an important role in the microsvasculopathy of type 2 diabetes,and sorbitol dehydrogenase (SDH) gene is involved in the pathogenesis of diabetic retinopathy(DR).There is no relevant research at home up to now.Objective This study was to investigate the correlation of sorbitol dehydrogenase (SDH) G-888C gene polymorphism with diabetic retinopathy (DR) in type 2 diabetes mellitus.Methods The SDH genotypes were determined by polymerase chain reactionreaction fragment length polymorphism (PCR-RFLP) in 187 patients with diabetes and 123 normal contrels.Patients were divided into two groups depending on the presence or absence of DR(DR:n=118;NDR:n=69).The frequencies of SDH genotype and allele were assayed and compared among these groups.This study was approved by Ethic Committee of Guangdong General Hospital.Written informed consent was obtained from each individual prior to any relevant medical procedure.Results The disease course in the DR group was significantly longer than that in NDR group(t=2.070,P=0.042),and other clinical features in both groups were non-significant (all P>0.05).The genotype frequencies in the DR group,NDR group and normal control group were 24.6%,8.7% and 8.1%,respectively,and frequencies of the G allele were 42.4%,25.4% and 29.7%,showing statistically significant differences among these three groups.The GG genotype and G allele frequencies were significantly higher in the DR group than those in the NDR group and normal control group (GG:P=0.007,P=0.001;G:P=0.001,P=0.004).There were no significant differences in the frequencies of the GG genotype and G allele between the NDB group and normal control group ( P>0. 05) as well as the proliferative DR group and non-proliferative DR group (P>0.05).Conclusion SDH G-888C gene polymorphism is associated with the development of diabetic retinopathy in southern Chinese.