Sugar synthesis in Leptospira. II. Presence of glyoxylate cycle enzymes

Screening and confirmatory analysis of glyoxylate: a biomarker of plants resistance against herbicides

The evidence that glyoxylate is a biomarker of tolerance or susceptibility to the action of herbicides belonging to the glycine family makes necessary to develop simple methods for the determination of this metabolite. Glyoxylate level allows both to know the presence/absence of members of the glycine family in plants and plant response to these herbicides. With this aim, a colorimetric-screening method has been developed for determination of glyoxylate based on formation of a phenylhydrazone, then oxidised to red coloured 1,5-diphenylformazan. Simultaneous optimization of ultrasound-assisted extraction of glyoxylate from plants and derivatization by a multivariate design has allowed the determination of the target analyte in fresh plants without interferences from pheophytines and compounds with carbonyl groups. Limits of detection and quantification are 0.05 μg ml(-1) and 0.17 μg ml(-1), respectively, with precision, expressed as relative standard deviation, of 3.3% for repeatability and 5.6% for the within-day laboratory reproducibility. Only 50mg of plant is necessary for determination of glyoxylate within 32 min. Confirmatory analysis by capillary electrophoresis-diode array detection in samples of Lolium spp. subjected to treatment with glyphosate shows that the relative error of the proposed method is always lower than 7%.

Phospholipases of Leptospira. I. Presence of phospholipase A1 and lysophospholipase in Leptospira biflexa

The hydrolysis of phosphatidylethanolamine, phosphatidylcholine, lysophosphatidylcholine, and trioleoylglycerol by Leptospira biflexa strain Urawa was studied in vitro. Phospholipase A1 was identified by the formation of 32P- and 14C-labeled lysoderivatives from 32P-phosphatidylcholine, 32P-phosphatidylethanolamine, or 1-acyl-2-[1-14C]oleoyl-sn-glycero-3-phosphorylcholine. Phospholipase A1 activity was independent of lipase in the microorganism since 14C-labeled trioleoylglycerol was scarcely attacked under the same conditions in which the phospholipids were hydrolyzed. Lysophospholipase activity was also demonstrated using 32P- and non-labeled lysophosphatidylcholine. The activity of phospholipase A1 was found in a broad range of pH but no optimal pH was determined. The pH optimum of lysophospholipase was 8.0. Both enzymes were labile to heat. Phospholipase C activity, however, could not be detected because no radioactive di- and monoacylglycerol was found in the experiment with 1-acyl-2-[1-14C]-oleoyl-sn-glycero-3-phosphorylcholine as the substrate. It was inferred that phosphatidylethanolamine, which was the major component of phospholipids in leptospirae, was hydrolyzed serially by phospholipase A (A1 and/or A2?) and lysophospholipase to glycerophosphorylethanolamine via 2-acyl-type-lyso-derivative as one metabolic pathway of the substrate.

Sugar synthesis in Leptospira. I. Presence of glucosephosphate isomerase

The presence of glucosephosphate isomerase, one of the key enzymes in carbohydrate metabolism, was confirmed for the first time in the cell-free extract of Leptospira biflexa. The glucosephosphate isomerase of L. biflexa was heat-labile and its optimum pH was about 8.5. The enzyme showed an optimal temperature of about 45 C but was more stable at 30 C. Km value of the enzyme was 5.6 X 10(-3)M. The activity of the enzyme was inhibited by the inhibitor, 6-phosphogluconate. From this study, the presence of a metabolic pathway, the phosphogluconate pathway, other than non-oxidative pentose phosphate pathway presented by Baseman and Cox was suggested.