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Results for “Enzyme stabilization”

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At least 109 records · Page 6Linked to original sources
PubMed1985

Rat lingual lipase: effect of proteases, bile, and pH on enzyme stability.

In addition to initiating fat digestion in the stomach, lingual lipase may play a significant digestive role in the upper small intestine. By in vitro incubation techniques, the stability of rat lingual lipase at various physiological pH values, as well as the effects of pure proteases, rat gastric juice, bile, pancreatic juice, and mixed duodenal contents, on enzyme activity was explored. There were no changes in base-line activity of porcine pepsin, bovine carboxypeptidase-treated lipase, or heat-denatured proteases compared with controls after incubation at pH 2-6 at 37 degrees C for up to 1 h. In contrast, porcine trypsin-treated lipase demonstrated a significant loss from base-line activity to 59 +/- 12% (mean +/- SE) at pH 4, 34 +/- 11% at pH 6, and 41 +/- 4% at pH 8, and bovine chymotrypsin caused a loss in lipase activity to 11 +/- 7% at pH 8. Rat gastric juice containing 5,000 U pepsin reduced lipase activity to 17 +/- 5% of initial activity at pH 2 and to 45 +/- 3% at pH 4. Rat bile alone diminished activity only 35%, but rat pancreatic juice or mixed duodenal juice reduced lingual lipase activity to 1-12% of initial activity after 60 min at pH 6. Lingual lipase is particularly important in fat digestion in the stomach; however, its role in quantitative fat digestion under small intestinal conditions may be limited.

Animals↗
PubMed1980

Purification and enzyme stability of alcohol dehydrogenase from Drosophila simulans, Drosophila virilis and Drosophila melanogaster adhS.

Three alcohol dehydrogenases from Drosophila simulans, Drosophila virillis and Drosophila melanogaster adhS (which possesses an alloenzyme with slow electrophoretic mobility) were purified essentially to homogeneity. The purification procedure involves a new step of affinity chromatography, which efficiently lowers the amount of contaminants in the final preparation, producing a very stable enzyme. The purification procedure developed consists of a salmine sulphate precipitation, two CM-Sepharose CL-6B colume-chromatography steps, an affinity-chromatography step and a Sephacryl gel filtration. A minimum of 30-fold purification is obtained and the yield is not less than 34%. The isoelectric points and molar absorption coefficients were determined.

Alcohol Oxidoreductases↗
PubMedDate not supplied

The enzyme stability of dehydro-enkephalins.

Dehydro-enkephalins [delta Ala2]-, [delta Ala3]-, [delta Phe4]-, and [delta Leu5]enkephalins, were examined for their stability to enzymatic hydrolysis by carboxypeptidase Y [EC 3.4.16.1]. The successively liberated amino acids were determined quantitatively by amino acid analyses. The saturated leucine-enkephalin was rapidly hydrolyzed from the COOH-terminus. However, peptide linkages with alpha, beta-dehydroamino acid residues placed in the enkephalin molecule were strongly resistant to the enzyme at the carboxyl side and completely resistant at the amino side of the dehydro residue.

Amino Acids↗
PubMed1981

Radioenzymic measurement of norepinephrine, epinephrine, and dopamine: stability, enzymic activity, and sensitivity.

We investigated factors affecting sensitivity and reproducibility of radioenzymic (catechol-O-methyltransferase) measurement of plasma catecholamines. There was no apparent deterioration of catecholamine during storage at -20 degrees C for 240 days. Accuracy and sensitivity of the assay depended mostly on the method of transferase preparation; its preparation by adjusting the pH to 6.8 before fractionation with ammonium sulfate resulted in an unsuitable enzyme with a relatively high background-radioactivity count, particularly for neorepinephrine and dopamine.

Catechol O-Methyltransferase↗
PubMed1992

Enzyme stability in downstream processing. Part 2: quantification of inactivation.

In biotechnological recovery processes the instability of the product can lead to large losses in the sequence of recovery processes needed to purify the product. As the cost of the final active product is strongly dependent on the recovery yield, this will lead to an increase in product cost. Therefore knowledge of factors that influence stability is important. This Part 2 provides the basic principles for design and operation of processes in which inactivation takes place. Simple kinetics and reactor modelling are discussed. These are applied to a number of unit operations: cell disruption, membrane filtration, drying and reversed micellar extraction. It is thus shown that the basic tools for modeling of biochemical processes provide us with the data needed for optimal process design and operation.

Journal Article↗
PubMedDate not supplied

Cefoperazone: a review of its antimicrobial spectrum, beta-lactamase stability, enzyme inhibition, and other in vitro characteristics.

The in vitro qualities of cefoperazone were reviewed on the basis of international medical literature and some new observations. Cefoperazone is highly active against the Enterobacteriaceae. Its activity against Staphylococcus aureus is comparable to that of the other newer cephem antibiotics. Cefoperazone is also active against all beta-hemolytic streptococci and Streptococcus pneumoniae and is relatively inactive against methicillin-resistant S. aureus and enterococci. Against Pseudomonas aeruginosa cefoperazone is at least fourfold more active than cefotaxime or moxalactam and is approximately as active as azlocillin or piperacillin. Haemophilus and Neisseria species, regardless of beta-lactamase production, are highly susceptible to cefoperazone. Against the Bacteroides fragilis group, cefoperazone is either very active or quite inactive because of endemic variations. The drug is slightly less stable to some beta-lactamases than are cefotaxime-like or 7-methoxy cephem drugs. Cefoperazone is a bactericidal beta-lactam, and its minimal inhibitory concentrations are influenced only by high inoculum concentrations of beta-lactamase-producing strains. Its ability to permeate bacterial cell membranes appears similar to that of cefotaxime. Synergy studies with cefoperazone plus beta-lactamase inhibitors or aminoglycosides against Enterobacteriaceae and P. aeruginosa show enhanced killing. Cefoperazone is 70%-94% protein bound and has high affinities for bacterial penicillin-binding proteins 3, 1a, 2, and 1 bs.

Anaerobiosis↗