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

In adult sparse-fur mutant mice, ornithine transcarbamylase (OTC) activity represents only 14% of the normal values. We studied the development of this activity from birth to adult period and demonstrated that the enzyme deficiency is already fully expressed at birth, in both the liver and the small intestine of mutants. Since OTC catalyzes the conversion of ornithine to citrulline, in the presence of carbamoyl-phosphate, the effect of a disturbed ornithine metabolism on the postnatal development of the small intestine has been evaluated. The normal appearance of sucrase as well as the normal increase of glucoamylase, trehalase, and alkaline phosphatase activities are delayed in sparse-fur mice compared with controls. Moreover, normal adult values are never attained. In contrast, the normal decline of lactase activity is impaired while leucylnaphthylamidase activity is unaffected. Cell proliferation, as evaluated by [3H]thymidine incorporation into DNA and mitotic index, is less active during the 3rd wk of life in mutants. These phenomena are closely associated with a transient weak arginase and ornithine decarboxylase activity in the small intestine. Since arginase catalyzes the conversion of arginine to orthithine, thus ensuring the availability of this substrate for ornithine decarboxylase activity, these results indicate a disturbance of polyamine metabolism in mutant enterocytes with a consequent delay in postnatal differentiation and proliferation. Sparse-fur mutant mouse may therefore represent a useful animal model for evaluating the role of ornithine metabolism in the maturation process of the small intestine.
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PMID:Postnatal maturation of enterocytes in sparse-fur mutant mice. 395 97

The enzyme responsible for all of the isomaltase activity and much of the maltase activity in the small intestine of the Californian sea lion (Zalophus californianus) was isolated by detergent solubilization of the brush-border membrane, followed by immunoadsorption chromatography using antibodies directed against rabbit sucrase-isomaltase. In 0.1% Triton X-100, sea lion isomaltase occurs as a monomer of Mr = 245,000 and is composed of a single polypeptide chain. As judged from the stoichiometry of the covalent binding of the affinity label, conduritol-B-epoxide, this polypeptide chain carries two enzymatically active sites; they are apparently identical and do not show either positive or negative cooperativity. In addition to cross-reacting immunologically with rabbit sucrase-isomaltase, sea lion isomaltase has similar overall enzymatic properties, with the exception of not hydrolyzing sucrose. The Alaskan fur seal (Collarhinus ursinus) has a two-active site isomaltase; however, in contrast to the sea lion, this animal is endowed with a small but significant sucrase activity. Along with (fully active) pro-sucrase-isomaltase, sea lion isomaltase is one of the very few examples of enzymes with more than one active site on a single polypeptide chain acting "in parallel" (rather than "in series"). Furthermore, this enzyme triggers some interesting questions on the phylogenetical pedigree of small intestinal sucrase-isomaltase.
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PMID:A two-active site one-polypeptide enzyme: the isomaltase from sea lion small intestinal brush-border membrane. Its possible phylogenetic relationship with sucrase-isomaltase. 671 26

An autoselection system for increasing plasmid stability in Kluyveromyces lactis, based on the blockage of the pyrimidine de novo and salvage pathways, was investigated. In a manner analogous to that used in Saccharomyces cerevisiae, a putative "fur 1" mutation was selected in a uraA K. lactis strain using 5-fluorouracil and 5-fluorocytosine plates. Survival of the mutant required expression of a plasmid-borne URA3 gene regardless of the culture medium employed, verifying the efficacy of this autoselection system in K. lactis. The expression of heterologous invertase, encoded by the S. cerevisiae SUC2 gene, was studied during long-term sequential batch cultures (70 generations) in complex yeast/peptone/glucose medium. The fur 1 mutant successfully retained the plasmid; invertase specific activity remained above 90% of the initial level. Furthermore, no mutation reversion was observed. In contrast, for the control non-fur 1 strain, only 4% of the cells retained the plasmid after 70 generations, and invertase specific activity dropped to less than 10% of the initial level. Experiments comparing growth and activity in different media indicated the potential for improving productivity through medium enrichment using this autoselection system.
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PMID:An autoselection system in recombinant Kluyveromyces lactis enhances cloned gene stability and provides freedom in medium selection. 953 54