The uncharacterized gene previously proposed as a mannose-6-phosphate isomerase from Bacillus subtilis was cloned and expressed in Escherichia coli. The maximal activity of the recombinant enzyme was observed at pH 7.5 and 40°C in the presence of 0.5 mM Co 2؉ . The isomerization activity was specific for aldose substrates possessing hydroxyl groups oriented in the same direction at the C-2 and C-3 positions, such as the D and L forms of ribose, lyxose, talose, mannose, and allose. The enzyme exhibited the highest activity for L-ribulose among all pentoses and hexoses. Thus, L-ribose, as a potential starting material for many L-nucleoside-based pharmaceutical compounds, was produced at 213 g/liter from 300-g/liter L-ribulose by mannose-6-phosphate isomerase at 40°C for 3 h, with a conversion yield of 71% and a volumetric productivity of 71 g liter ؊1 h ؊1 .L-Ribose is a potential starting material for the synthesis of many L-nucleoside-based pharmaceutical compounds, and it is not abundant in nature (5, 19). L-Ribose has been produced mainly by chemical synthesis from L-arabinose, L-xylose, Dglucose, D-galactose, D-ribose, or D-mannono-1,4-lactone (2,17,23). Biological L-ribose manufacture has been investigated using ribitol or L-ribulose. Recently, L-ribose was produced from ribitol by a recombinant Escherichia coli containing an NAD-dependent mannitol-1-dehydrogenase (MDH) with a 55% conversion yield when 100 g/liter ribitol was used in a 72-h fermentation (18). However, the volumetric productivity of L-ribose in the fermentation is 28-fold lower than that of the chemical method synthesized from L-arabinose (8). L-Ribulose has been biochemically converted from L-ribose using an Lribose isomerase from an Acinetobacter sp. (9), an L-arabinose isomerase mutant from Escherichia coli (4), a D-xylose isomerase mutant from Actinoplanes missouriensis (14), and a D-lyxose isomerase from Cohnella laeviribosi (3), indicating that L-ribose can be produced from L-ribulose by these enzymes. However, the enzymatic production of L-ribulose is slow, and the enzymatic production of L-ribose from L-ribulose has been not reported.Sugar phosphate isomerases, such as ribose-5-phosphate isomerase, glucose-6-phosphate isomerase, and galactose-6-phosphate isomerase, work as general aldose-ketose isomerases and are useful tools for producing rare sugars, because they convert the substrate sugar phosphates and the substrate sugars without phosphate to have a similar configuration (11,12,21,22). L-Ribose isomerase from an Acinetobacter sp. (9) and D-lyxose isomerase from C. laeviribosi (3) had activity with L-ribose, D-lyxose, and D-mannose. Thus, we can apply mannose-6-phosphate (EC 5.3.1.8) isomerase to the production of L-ribose, because there are no sugar phosphate isomerases relating to L-ribose and D-lyxose. The production of the expensive sugar L-ribose (bulk price, $1,000/kg) from the rare sugar L-ribulose by mannose-6-phosphate isomerase may prove to be a valuable industrial process, because we have produced Lribulose from the ch...

Aims: To perform a systematic evaluation of the applicability, validity and reliability of the long PCR-RFLP of 16S-ITS-23S rRNA genes for bacterial genotyping using both sequences retrieved from public genome databases and the experimental data obtained on bacterial cultures. Methods and Results: 3301 Full-length sequences of 16S-ITS-23S rRNA genes were retrieved from 885 published bacterial genomes. Copy numbers of the whole set of 16S-ITS-23S rRNA genes per genome ranged from 1 (n = 161) to 14 (n = 4) with an average of 3Á71. Their length varied greatly, from 4319 to 6568 bp with an average of 4952 bp. Computer-simulated RFLP analyses of the 16S-ITS-23S fragments flanked by the conserved primers 27F and 2241R suggested MspI, RsaI, HhaI and TaqI as the most appropriate enzymes for long PCR-RFLP analysis of the 16S-ITS-23S sequence. MspI was used to screen over 900 bacterial cultures isolated from the Huguangyan Maar Lake in southern China. An experimental sequencing of 16S rRNA genes of the isolates possessing a unique RFLP band pattern proved the broad applicability and high resolution of this approach. Conclusions: These results indicate that long PCR-RFLP of 16S-ITS-23S rRNA genes is a potentially universal and reliable bacterial genotyping tool with a high resolution. Significance and Impact of the Study: The methodology of long PCR-RFLP of 16S-ITS-23S rRNA genes will facilitate the exploration and tracing of cultivable microbial diversity in natural environments.

Geobacillus thermodenitrificans, with a double-site mutation in L-arabinose isomerase, produced 95 g L-ribulose l(-1 ) from 500 g L-arabinose l(-1) under optimum conditions of pH 8, 70 degrees C, and 10 units enzyme ml(-1) with a conversion yield of 19% over 2 h. The half-lives of the mutated enzyme at 70 and 75 degrees C were 35 and 4.5 h, respectively.

The phytopathogenic enterobacterium Erwinia chrysanthemi secretes a number of enzymes involved in plant-tissue degradation, notably the five isoenzymes of pectate lyase. We have cloned a region involved in pectate lyase and cellulase secretion by complementation of non-secretory outJ mutants of E. chrysanthemi strain 3937 using the RP4::miniMu plasmid pULB110. The cloned region maps near the ade-22 marker on the E. chrysanthemi 3937 chromosome. An R-prime containing a chromosomal DNA insert of about 30kb was first obtained; subcloning into pBR325 permitted the isolation of a 4kb ClaI/SspI fragment able to complement outJ mutations in E. chrysanthemi. The isolation of phoA fusions in this fragment allowed us to determine the direction of transcription of the encoding region, which extends over about 2.5kb, and demonstrate that this region encodes exported protein(s). When the TnphoA insertions were transferred back into E. chrysanthemi chromosome, the recombined strains no longer secreted pectate lyases or cellulases. Identification of the products encoded by the ClaI/SspI fragment demonstrated that outJ encodes an 83 kD polypeptide which is processed to an 81 kD polypeptide by cleavage of a signal sequence. The cloned DNA fragment did not endow Escherichia coli with the ability to secrete pectate lyases.

Phlorizin is the most abundant glucoside of phloretin from the apple tree and its products. Phlorizin and its aglycone phloretin are currently considered health-beneficial polyphenols from apples useful in treating hyperglycemia and obesity. Recently, we showed that phloretin could be regioselectively hydroxylated to make 3-OH phloretin by Bacillus megaterium CYP102A1 and human P450 enzymes. The 3-OH phloretin has a potent inhibitory effect on differentiating 3T3-L1 preadipocytes into adipocytes and lipid accumulation. The glucoside of 3-OH phloretin would be a promising agent with increased bioavailability and water solubility compared with its aglycone. However, procedures to make 3-OH phlorizin, a glucoside of 3-OH phloretin, using chemical methods, are not currently available. Here, a biocatalytic strategy for the efficient synthesis of a possibly valuable hydroxylated product, 3-OH phlorizin, was developed via CYP102A1-catalyzed regioselective hydroxylation. The production of 3-OH phlorizin by CYP102A1 was confirmed by HPLC and LC–MS spectroscopy in addition to enzymatic removal of its glucose moiety for comparison to 3-OH phloretin. Taken together, in this study, we found a panel of mutants from B. megaterium CYP102A1 could catalyze regioselective hydroxylation of phlorizin to produce 3-OH phlorizin, a catechol product.