Regulatory role of GDP in the phosphoenzyme formation of guanine nucleotide: Specific forms of succinyl coenzyme a synthetase

We have previously shown that micromolar concentrations of GDP stimulate the GTP-mediated phosphorylation of p36, the subunit of succinyl-CoA synthetase (SCS), in lysates prepared fromDictyostelium discoideum. In this study, we report that this phenomenon represents an enhanced catalytic capacity of SCS to form the phosphoenzyme intermediate. Low concentrations of GDP stimulate phosphoenzyme formation by either GTP, or succinyl-CoA and P_i. Under these conditions GDP enhances the apparent rate of phosphoenzyme formation but does not significantly alter the fraction of phosphorylated enzyme. This effect is retained during purification of the protein and is also observed with purified pig heart SCS, indicating that GDP directly alters the enzyme to enhance its rate of phosphorylation. Under these conditions, GDP does not function at the catalytic site, implying an allosteric regulation of SCS.Abbreviations used SCS succinyl-CoA synthetase - P _i inorganic phosphate - NDP nucleotide diphosphate - NTP nucleotide triphosphate - PFK phosphofructokinase A-form; ADP-forming SCS; G-form; GDP-forming SCS     

Butanol production from thin stillage using Clostridium pasteurianum

The production of butanol from thin stillage by Clostridium pasteurianum DSM 525 was evaluated in the paper. At initial pH values ranging from 5.0 to 7.0 C. pasteurianum DSM 525 produced 6.2-7.2 g/L of butanol utilizing glycerol in thin stillage as the main carbon source, with yields of 0.32-0.44 g butanol produced/g glycerol consumed, which are higher than previously reported yields (e.g., 0.14-0.31 g butanol/g glycerol, Biebl, 2001). Lactic acid in the thin stillage acted as a buffering agent, maintaining the pH of the medium within a range of 5.7-6.1. Lactic acid was also utilized along with glycerol, enhancing butanol production (6.5 g/L butanol vs. 8.7 g/L butanol with 0 and 16 g/L lactic acid, respectively). These results demonstrate the feasibility of cost-effective butanol production using thin stillage as a nutrient-containing medium with a pH buffering capacity.     

Mycobacterium ulcerans Persistence at a Village Water Source of Buruli Ulcer Patients

Buruli ulcer (BU), a neglected tropical disease of the skin and subcutaneous tissue, is caused by Mycobacterium ulcerans and is the third most common mycobacterial disease after tuberculosis and leprosy. While there is a strong association of the occurrence of the disease with stagnant or slow flowing water bodies, the exact mode of transmission of BU is not clear. M. ulcerans has emerged from the environmental fish pathogen M. marinum by acquisition of a virulence plasmid encoding the enzymes required for the production of the cytotoxic macrolide toxin mycolactone, which is a key factor in the pathogenesis of BU. Comparative genomic studies have further shown extensive pseudogene formation and downsizing of the M. ulcerans genome, indicative for an adaptation to a more stable ecological niche. This has raised the question whether this pathogen is still present in water-associated environmental reservoirs. Here we show persistence of M. ulcerans specific DNA sequences over a period of more than two years at a water contact location of BU patients in an endemic village of Cameroon. At defined positions in a shallow water hole used by the villagers for washing and bathing, detritus remained consistently positive for M. ulcerans DNA. The observed mean real-time PCR Ct difference of 1.45 between the insertion sequences IS2606 and IS2404 indicated that lineage 3 M. ulcerans, which cause human disease, persisted in this environment after successful treatment of all local patients. Underwater decaying organic matter may therefore represent a reservoir of M. ulcerans for direct infection of skin lesions or vector-associated transmission.     

Short-term Administration of Water-soluble Silicon Improves Mineral Density of the Femur and Tibia in Ovariectomized Rats

Silicon is important for the proper growth and development of bone and connective tissues. This study was designed to investigate if water-soluble silicon could be used for the treatment of postmenopausal osteoporosis. Silicon (Si 20 mg/kg body weight/day) was administrated orally to 17-week-old ovariectomized (OVX) rats for 4 weeks. Silicon did not alter weight gain in OVX rats. Silicon supplementation significantly increased the bone mineral density of the femur (p < 0.05, vs. OVX control group) and tibia in OVX rats (p < 0.05, vs. OVX control group). Serum alkaline phosphatase and osteocalcin, two bone formation biomarkers tested, were not significantly altered, but urinary calcium and phosphorous excretion tended to decrease with silicon supplementation. OVX rats with silicon supplementation showed a relatively higher serum CTx compared to the nonsupplemented OVX group (p < 0.01, vs. OVX control group). According to these results, short-term soluble silicon supplementation improved bone mineral density in OVX-induced osteoporosis.     

Absolute configuration-dependent epoxide formation from isoflavan-4-ol stereoisomers by biphenyl dioxygenase of Pseudomonas pseudoalcaligenes strain KF707

Biphenyl dioxygenase from Pseudomonas pseudoalcaligenes strain KF707 expressed in Escherichia coli was found to exhibit monooxygenase activity toward four stereoisomers of isoflavan-4-ol. LC-MS and LC-NMR analyses of the metabolites revealed that the corresponding epoxides formed between C2' and C3' on the B-ring of each isoflavan-4-ol substrate were the sole products. The relative reactivity of the stereoisomers was found to be in the order: (3S,4S)-cis-isoflavan-4-ol > (3R,4S)-trans-isoflavan-4-ol > (3S,4R)-trans-isoflavan-4-ol > (3R,4R)-cis-isoflavan-4-ol and this likely depended upon the absolute configuration of the 4-OH group on the isoflavanols, as explained by an enzyme-substrate docking study. The epoxides produced from isoflavan-4-ols by P. pseudoalcaligenes strain KF707 were further abiotically transformed into pterocarpan, the molecular structure of which is commonly found as part of plant-protective phytoalexins, such as maackiain from Cicer arietinum and medicarpin from Medicago sativa.