CHARACTERIZATION OF LEPTOSPIRAL LIPASE

Enzyme patterns in the study of leptospira

An analysis of intracellular and extracellular leptospiral enzymes was made by use of starch-gel electrophoresis with natural and synthetic substrates. Of 37 serotypes examined for extracellular exterase, all had activity of varying mobility and degree. All extracellular preparations were negative for catalase, phosphatase, and naphthylamidase. Intracellularly, five serotypes were examined, including Leptospira biflexa Patoc I, L. biflexa Waz, L. canicola Moulton, L. icterohaemorrhagiae RGA, and L. pomona S91. Among the enzymes detected by this electrophoretic technique were transaminase and catalase, confirming the results of previous investigators. Further, other enzymes heretofore unreported have been detected. These include esterases, phosphatases, lactic, malic, glutamic, succinic, alpha-glycerophosphate, and 6-phosphogluconic dehydrogenases, and a naphthylamidase. The presence of these enzymes suggests the existence of tricarboxylic acid, glycolytic, and pentose-related pathways in Leptospira. In addition, enzyme patterns show promise in leptospiral classification.

Evaluation of a fluorimetric assay on the lipases from strains of milk psychrotrophic bacteria

A fluorimetric assay, developed for the assay in milk of the lipase of the raw milk psychrotrophPseudomonas fluorescensAR11 (Stead, 1983), was evaluated in both buffer and in milk using cell-free lipase preparations from 11 strains of lipolytic psychrotrophic bacteria isolated from milk. Lipases of all strains were more active against 4-methylumbelliferyl nonanoate (4-MUN) than against 4-methylumbelliferyl oleate (4-MUO) in the buffer system but most were less active against 4-MUN than against 4-MUO in the milk assay system. In both systems, 4-MUO had a much lower rate of non-enzymic hydrolysis than did 4-MUN. Lipase activities measured by radial diffusion in tributyrin agar and trioctanoin agar reflected activities against 4-MUO and 4-MUN, except that lipase from a strain of coliform was relatively more reactive against the 4-MU esters. When compared with assay in the buffer system the most effectively activated lipase in the milk system was that from AR11; of those from other strains, 6 were 50–69% as effectively activated, 2 were about 17% and 2 were 7–8% activated. This difference in behaviour was related to the direct inhibition of lipases of some of the strains by the mixture of sodium taurocholate (NaTC) and cetyltrimethylammonium bromide (CTAB) needed in the milk assay system to dissociate lipase from milk protein. Increasing the proportion of NaTC to CTAB increased the activities of the more weakly activated lipases but decreased those of others. The assay in milk may therefore underestimate the lipase from certain strains of psychrotrophic bacteria.

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.

Bovine pancreatic lipase. II. Stability and effect of activators and inhibitors

Purified bovine pancreatic lipase was highly unstable at and above refrigeration temperature. However, it could be stored frozen without loss of activity. Milk solids had some protective effect upon the enzyme against gamma-irradiation. Low concentrations of sodium, calcium, and magnesium salts stimulated lipolytic activity. However, heavy metal salts, such as ferric, cupric, and mercuric chlorides, were highly inhibitory. The bovine pancreatic lipase appeared to contain sulfhydryl groups which may be essential for the lipolytic activity since p-chloromercuribenzoate, N-ethylmaleimide, sodium arsenite, and iodoacetate inhibited the enzyme. A comparison of bovine pancreatic lipase and milk lipase revealed that the two enzymes were similar in thermal stability and effect of some of the activators and inhibitors on lipolytic activity.

Bovine pancreatic lipase.I.Isolation, homogeneity, and characterization

Bovine pancreatic lipase was isolated in pure form by lyophilization of fresh bovine pancreas, extraction of the enzyme with sucrose solution, fractional precipitation with ammonium sulfate and acetone, followed by chromatography on Sephadex G-100. The specific activity of the purest lipase fraction was 1750 micromoles fatty acid, liberated in 30 min per milligram of protein, indicating a purification of approximately 473-fold, with an overall yield of about 42%. Homogeneity of the enzyme was confirmed by rechromatography on Sephadex G-100 as well as with the gel electrophoretic and ultracentrifugal techniques. The purified enzyme gave a typical protein ultraviolet absorption spectrum with maximum absorption at 276 nm and minimum at 252 nm. The purified enzyme exhibited a single pH optimum of 8.8 and an isoelectric point near pH 5.5. Its optimum temperature was 37 C, and its optimum substrate concentration was 10%. These properties resembled those of milk lipase.

Lipid catabolism of relapsing fever borreliae

Relapsing fever borreliae require lipid compounds for growth in vitro. In this study, the major pathways of lipid catabolism in three species of tick-borne relapsing fever borreliae were investigated. Thin-layer chromatography was used to compare chloroform-methanol extracts of fresh culture media with extracts of exhausted culture media after organisms were removed by centrifugation. The chromatographic data demonstrated that lysolecithin was removed from the culture media during growth of the spirochetes, whereas lecithin, sphingomyelin, triglycerides, and cholesterol esters were not affected by growth of the organisms. Sonic extracts of the organism were tested for the presence of specific enzymes of lipid catabolism. Lysolecithinase, glycerophosphorylcholine diesterase, and acid phosphatase activities were demonstrated. Thus, these organisms can sequentially dissimilate lysolecithin to fatty acids, choline, inorganic phosphate, and glycerol. Assays for phospholipases A, C, and D, alpha-glycerophosphate dehydrogenase, alkaline phosphatase, and lipase were negative.

Estrutura antigênica e constituição química das leptospiras

Os autores fazem um estudo comparativo entre os métodos de sedimentação, MIF-C e Kato em relação à eficiência para diagnosticar ovos de helmintos, em especial os de Schistosoma mansoni. Discutem as possibilidades e limitações dos métodos assinalados e concluem pela maior eficiência do método de sedimentação.

Partial purification of an extracellular leptospiral lipase

Sequential procedures involving ethanol precipitation, ultracentrifugation, and molecular sieve chromatography in deoxycholate permitted 140-fold purification of a leptospiral lipase.

Lipase of Mucor pusillus

Lipase of Mucor pusillus NRRL 2543 was recovered with ammonium sulfate precipitation, gel filtration on Sephadex G-75, and anion-exchange chromatography on diethylaminoethyl-Sephadex A-50. Maximal glycerol ester hydrolase (lipase) activity was observed at pH 5.0 to 5.5 and 50 C when trioctanoin and olive oil were used as substrates. The enzyme also showed esterase activity; it hydrolyzed, with the exception of methyl butyrate, all methyl esters tested. A minimum chain length of six carbons appeared to be a requirement for esterase activity, which was maximal at about pH 5.5 with methyl dodecanoate (C(12)) as the substrate. Neither the glycerol ester hydrolase (lipase) nor the esterase activity of the enzyme appeared to be affected by thiol group inhibitors, chelating agents, and reducing compounds. On the other hand, hydrolysis of triolein and methyl dodecanoate was arrested to the same extent in the presence of diisopropyl fluorophosphate, which suggested the involvement of serine in the active center of the enzyme. The enzyme remained stable during a 30-day storage at - 10 C.

Density-gradient and chromatographic fraction of leptospiral lipase

Fractionation of leptospiral lipase by CsCl density gradients and G-200 Sephadex chromatography yielded five active protein peaks. Two were obtained from the density gradients and three from G-200 Sephadex columns. Esterase activity of these fractions was demonstrated by electrophoretic examination. Several protein bands were visible when disc electrophoresis was performed on the respective fractions. Lipolytic and esterolytic activities were both present, and the overlapping of these activities was discussed.

Intermediate energy metabolism of Leptospira

Metabolic studies were performed on three representative serotypes of Leptospira: a water isolate designated B(16) and two pathogenic serotypes, pomona and schueffneri. Examination of whole cells of B(16) for their ability to oxidize various substrates revealed that oleate significantly stimulated oxygen uptake. The respiratory quotient of 0.7 implied that oleate was degraded to carbon dioxide and water. Other substrates, such as carbohydrates, alcohols, intermediates of the citric acid cycle, and short-chain acids, including selected amino acids, did not stimulate endogenous respiration of whole cells. No oxygen uptake could be measured when cell-free extracts were tested with the substrates used with whole cells. Enzymatic analyses of cell-free extracts of the three strains demonstrated enzymes of the citric acid cycle, enzymes of the glycolytic and pentose pathways, and the general acyl coenzyme A dehydrogenase required for beta-oxidation of fatty acids. Strain B(16) and the two pathogenic serotypes appeared to possess similar metabolic capabilities. Enzymatic data might also explain the apparent inability of B(16) to oxidize other substrates; kinases necessary for activation of common nonphosphorylated compounds were not detected in leptospiral extracts. These findings emphasized the dependence of leptospiral growth upon long-chain fatty acids.

Freeze-cutting of density gradients

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