Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A sucrase from honey bees (Apis mellifera) which precipitates between ammonium sulfate saturations of 50 and 70% (5 mg protein per millilitre) and which makes up the major portion of the sucrases of honey bees was purified to homogeneity as shown by several criteria. A large part of the sucrase was found in the head while most of the rest was in the abdomen (a small amount was in the thorax). The enzyme precipitated between the same values of ammonium sulfate saturation as did the sucrase in honey and honey sucrase exhibited kinetics very similar to those of this enzyme. The enzyme was found to be a relatively nonspecific alpha-glucosidase and was shown to have transglucosidase activity. The production of glucose from sucrose was rectilinear when plotted by the Hofstee method at low substrate concentrations but decreased at high sucrose concentrations. The production of fructose was rectilinear throughout the concentration range used. The production of both glucose and rho-nitrophenol when rho nitrophenyl alpha-D-glucoside was the substrate was linear by the Hofstee plot. These effects were found to be due to transglucolysis and a mechanism of action is proposed. Amino acid and amino sugar analyses indicated that the sucrase was a glycoprotein. The molecular weight was found to be between 51000 and 82000 by three different methods and an so20.w value of 4.0 S was obtained. There was no evidence for subunit structure. Tests of the enzyme under various denaturation conditions did not reveal any unusual stabilities. The sucrase bound very tightly to a hydrophobic column. Iodoacetic acid decreased the activity of the sucrase but a large concentration was needed to bring about a 50% activity loss. Reducing agents caused some activity declines. Diethyl pyrocarbonate activated the enzyme.
 ...
PMID:Physical, chemical, and enzymatic studies on the major sucrase of honey bees (Apis mellifera). 0 3

1. The effects on Neurospora crassa invertase (beta-D-fructofuranoside fructohydrolase, EC 3.2.1.26) of a variety of group specific reagnets and other potential inhibitors were determined during a search for an irreversible inhibitor of the enzyme. Aniline, pyridoxal, enzyme substrate and products did not inactivate invertase under reducing conditions. Bromoacetic acid, iodoacetic acid, iodoacetamide, p-chloromercuribenzoate, hydroxylamine and 2-hydroxy-5-nitrobenzyl bromide were also ineffective. Iodine was the only reagent which irreversibly inhibited invertase. 2. Invertase was rapidly inactivated by low concentrations of iodine, indicating specific inhibition. However, the enzyme could not be protected from this inactivation by substrate. It was not reactivated by mercaptoethanol or cysteine. 3. Experiments on the uptake of radioactive iodine demonstrated that invertase is not iodinated under the conditions of iodine inactivation. 4. The sedimentation (S20,w) value of invertase was not altered by iodine inactivation. One-dimensional electrophoresis and finger-printing of tryptic digests revealed no differences between iodine treated and untreated invertase. There was no loss of carbohydrate from this glycoprotein during iodine inactivation. 5. Standard amino acid analyses of iodine-inactivated invertase showed some loss of tyrosine and a trace amount of methionine sulfone. Attempts to demonstrate oxidation of methionine to the sulfone, through modification of the procedure for preparation of samples for analysis, were unsuccessful. However, oxidation of half-cystine was indicated and further loss of tyrosine noted. A hypothesis is advanced that half-cystine is oxidized by iodine to a normally unstable oxidation state which is maintained and protected by its protein invironment and that loss of tyrosine may be an artifact caused by the presence of this residue during acid hydrolysis.
 ...
PMID:Neurospora crassa invertase. A study of amino acids at the active center. 23 50

Acid trehalase was purified from the yeast suc2 deletion mutant. After hydrophobic interaction chromatography, the enzyme could be purified to a single band or peak by a further step of either polyacrylamide gel electrophoresis, gel filtration, or isoelectric focusing. An apparent molecular mass of 218,000 Da was calculated from gel filtration. Polyacrylamide gel electrophoresis of the purified enzyme in the presence of sodium dodecyl sulfate suggested a molecular mass of 216,000 Da. Endoglycosidase H digestion of the purified enzyme resulted after sodium dodecyl sulfate gel electrophoresis in one distinct band at 41,000 Da, representing the mannose-free protein moiety of acid trehalase. The carbohydrate content of the enzyme was 86%. Amino acid analysis indicated 354 residues/molecule of enzyme including 9 cysteine moieties and only 1 methionine. The isoelectric point of the enzyme was estimated by gel electrofocusing to be approximately 4.7. The catalytic activity showed a maximum at pH 4.5. The activity of the enzyme was not inhibited by 10 mM each of HgCl2, EDTA, iodoacetic acid, phenanthrolinium chloride or phenylmethylsulfonyl fluoride. There was no activation by divalent metal ions. The acid trehalase exhibited an apparent Km for trehalose of 4.7 +/- 0.1 mM and a Vmax of 99 mumol of trehalose min-1 X mg-1 at 37 degrees C and pH 4.5. The acid trehalase is located in the vacuoles. The rabbit antiserum raised against acid trehalase exhibited strong cross-reaction with purified invertase. These cross-reactions were removed by affinity chromatography using invertase coupled to CNBr-activated Sepharose 4B. Precipitation of acid trehalase activity was observed with the purified antiserum.
 ...
PMID:Purification and characterization of acid trehalase from the yeast suc2 mutant. 328 51