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R P Yadav

Publications and source records attributed to R P Yadav.

10 recordsLinked to original sources
PubMed1998

Lipase production by Aspergillus and Penicillium species.

Forty each of aspergilli and penicillia were screened for extracellular lipase production on agar plates and in liquid medium containing olive oil as substrate. Twenty-nine aspergilli and twenty-six penicillia produced lipase. Out of these, 19 aspergilli and 22 penicillia showed activity both on Nile blue sulfate and glycerol tributyrate agar plates while only 10 aspergilli and 4 penicillia showed a positive response to glycerol tributyrate agar alone. The screening revealed 11 Aspergillus spp. and 15 Penicillium spp. as new lipase producers. Pig fat as an economic substrate for lipase production was also investigated.

Animals↗
PubMed1998

Purification and characterization of a regiospecific lipase from Aspergillus terreus.

Aspergillus terreus lipase was purified to homogeneity with 18.0% yield. The specific activity of the enzyme increased from 20.80 to 250 U/mg of protein. Ion exchange on Q-Sepharose was highly effective in the purification process. The molecular mass of the purified enzyme was 41+/-1 kDa as determined by SDS/PAGE. The purified lipase showed excellent temperature tolerance (15-90 degreesC) and was highly thermostable, retaining 100% activity at 60 degreesC for 24 h. It showed good pH tolerance (3.0-12.0) and was stable over a pH range of 4.0-10.0 for 24 h. The activity of the enzyme was inhibited by ionic detergents, whereas non-ionic detergents stimulated enzyme activity. Mg2+ and Ca2+ ions stimulated lipase activity, whereas Co2+, Cu2+, Ni2+ and Fe3+ ions caused inhibition. The enzyme was unaffected by the metal chelator EDTA or by 2-mercaptoethanol and potassium ferrocyanide. At a concentration of 100 microM, 3,4-dichloroisocoumarin caused weak inhibition with 40% loss of activity, but diethyl p-nitrophenyl phosphate at the same concentration strongly inhibited enzyme activity (98.12% loss of activity), confirming that the A. terreus lipase is a serine hydrolase. The lipase was highly active on pig fat (151% relative activity) and groundnut oil (103% relative activity) and least active on kusum oil (18% relative activity). Extensive dialysis did not affect enzyme activity up to 168 h, suggesting the absence of any dialysable cofactor in the enzyme. The A. terreus lipase retained significant activity on freeze-drying and had a shelf-life of more than 6 months at room temperature. The A. terreus lipase exhibited 1,3-regiospecificity and was stable in various organic solvents.

Aspergillus↗
PubMed1996

Microbial lipases: production and applications.

Lipases occupy a prominent place among biocatalysts and have a wide spectrum of biotechnological applications. Lipases are unique as they hydrolyse fats into fatty acids and glycerol at the water-lipid interface and can reverse the reaction in non-aqueous media. The stability of these enzymes in organic solvents have pushed them into the frontier areas of organic synthesis leading to the designing of novel drugs, surfactants, bioactive compounds and oleochemicals. In addition, lipase-catalysed trans-esterification and inter-esterification reactions have been exploited in the fat industry. Looking into the wide scenario of lipase applications, commercialization of lipase production is a prime area of interest for microbiologists, process engineers and biochemists. Research carried out in this field has revealed that microbes, especially fungi and bacteria, are the tools of choice for commercial production. Recently, the structure determination of a few microbial lipases has widened our knowledge about the unique mechanism of catalysis of this enzyme.

Animals↗
PubMed1995

Rapid cytoreduction in childhood leukemic hyperleukocytosis by conservative therapy.

Childhood leukemic hyperleukocytosis poses a serious threat to life because of its associated metabolic complications. The present prospective trial utilized conservative management of childhood acute lymphoblastic leukemia with hyperleukocytosis (total white cell count equal or > 100 x 10(9)/L) by intravenous hydration, urinary alkalinization, and allopurinol presenting without severe life-threatening complications. The median reduction in WBC count was 81.51% (range: 66-98.8%) within a median period of 36 hours (range: 12-60 hours) following hospitalization. There were no failures or treatment related complications. Thus we conclude that in childhood acute lymphoblastic leukemia, hyperleukocytosis can be managed safely and effectively with intravenous hydration, urinary alkalinization, and allopurinol before starting any specific anti-leukemic chemotherapy avoiding risk-associated cranial irradiation, leukapheresis, and exchange transfusion.

Adolescent↗
PubMed1995

Humoral immune responses to the Plasmodium falciparum antigen Pf155 RESA in adults with differential clinical conditions from an Indian zone where malaria is endemic.

Ring infected erythrocyte surface antigen of Plasmodium falciparum (Pf155/RESA) has been considered as a vaccine candidate. However, the relative immunogenicity of this antigen has not been studied in Indian populations. Pf155/RESA was investigated for its immunogenicity by studying humoral immune responses against Pf155/RESA and Pf155/RESA derived peptides (P1, P2 representing immunodominant epitopes from the 3' and P3 from the 5' repeat regions) by erythrocyte membrane immunofluorescence (EMIF) assay and by enzyme linked immunosorbent assay (ELISA) in P. falciparum primed donors living in hyperendemic malarious areas (Orissa State, India) where P. falciparum infections are highly prevalent. Subjects of different clinical status namely acute (A), clinically immune (CI) and acute with history of repeated P. falciparum infections (R) were included in this study. All the donors were seropositive against the crude antigen. There was considerable variation in the responses among the donors. While humoral responses in the plasmas against the P2 peptide (EENV)4 were significantly higher in magnitude and in frequency in the CI donors than in the A donors, no positive response was seen in the R donors. The responses to the peptides P1 (EENVEHDA)2 and P3 (DDEHVEEPTVA)2 were poor both in the A and in the CI groups. Whereas, most of the R donors were seropositive against the P3. The present results indicate that Pf155/RESA contains B cell epitopes which were recognized differently by the immune system of individuals living in malaria-hyperendemic areas of India who have been primed by natural infection. Our studies also suggest that in order to investigate the possible functional role of a given antigen, study of immune responses against the antigen in donors of different clinical status may be useful.

Adult↗
PubMedDate not supplied

DNA-hydrolyzing autoantibodies.

Catalysis by antibodies could be a frequent phenomenon if the immune system generates a sufficiently diverse number of antibody-active sites, some of which may possess catalytic activity. A catalytic antibody can be expected to do more damage than one that simply binds antigen. The best biochemical marker of systemic lupus erythematosus (SLE) is presence of autoantibodies to DNA. In the present article, we describe the DNA-hydrolyzing activity of DNA-binding autoantibodies purified from SLE patients. The substrates employed were supercoiled plasmid, radiolabeled plasmid fragments, and oligonucleotides. Hydrolysis of DNA by the antibodies was indicated by the appearance of fragments visualized by ethidium bromide staining of agarose gels or autoradiography of polyacrylamide gels. Changes in linear dichroism values were also indicative of DNA hydrolysis. The antibody activity was purified by protein A-sepharose chromatography, high-performance liquid chromatography gel filtration, and DNA-affinity chromatography. Scrupulous control studies were done to demonstrate that DNA-hydrolyzing activity really belongs to the antibodies. Purified Fab fragments showed hydrolyzing activity, whereas the Fc fragment was inactive. The specificity of DNA cleavage was investigated, and the rate parameters of hydrolysis by antibodies and conventional nucleases were compared.

Antibodies↗