Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Porcine liver betaine-homocysteine methyltransferase (BHMT; EC) was purified to homogeneity, and the Michaelis constants for betaine, dimethylacetothetin, and L-homocysteine are 23, 155, and 32 microM, respectively. The maximum rate of catalysis is 47-fold greater using dimethylacetothetin as a methyl donor compared with betaine. Partial amino acid sequence of porcine BHMT was obtained, and inosine-containing redundant oligonucleotide primers were used to amplify an 815-base pair sequence of the porcine cDNA by polymerase chain reaction (PCR). Nondegenerate oligonucleotide primers based on the porcine cDNA were synthesized and used to isolate a 463-base pair fragment of the human cDNA by PCR. The human PCR DNA product was then used to screen a cDNA library by plaque hybridization, and cDNAs encoding human BHMT were isolated. The primary structure of the human cDNA is reported here, and the open reading frame encodes a 406-residue protein of Mr 44,969. The deduced amino acid sequence of human BHMT shows limited homology to bacterial vitamin B12-dependent methionine synthases (EC). A plasmid containing the human BHMT cDNA fused in frame to the N terminus of beta-galactosidase was transformed into Escherichia coli, and transformants expressed BHMT activity, an activity that is absent from wild type E. coli.
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PMID:Purification, kinetic properties, and cDNA cloning of mammalian betaine-homocysteine methyltransferase. 879 61

Protein energy malnutrition (PEM) is common in underprivileged populations in many parts of the world and results from diets deficient in protein (kwashiorkor) or protein and calories (marasmus). The literature documents renal tubular abnormalities in children with PEM. In PEM the reabsorption of amino acids and phosphate is defective. In many kidney disorders in which renal tubular function is impaired (e.g., diabetes, preeclampsia, nephrotic syndrome, sickle cell anemia), lysosomal enzymuria ensues. We compared the urinary excretion of the following five lysosomal enzymes in 31 Nigerian children with marasmus, kwashiorkor, or marasmic-kwashiorkor: beta-hexosaminidase, alpha-galactosidase, beta-galactosidase, beta-glucuronidase, and alpha-mannosidase. All of the protein energy malnourished children and the 18 age- and gender-matched controls were from the city of Jos, located in central Nigeria. In the severely malnourished children, the urine levels of all five lysosomal enzymes (expressed as units of enzyme activity per mg creatinine) were markedly increased. The greatest increases were seen with beta-hexosaminidase (16-fold) and beta-glucuronidase (14-fold). Routine clinical analyses also revealed that, relative to the control population, the sera of the 14 most severely malnourished patients contained 2- to 5-fold more vitamin B12 and markedly reduced levels (15%, p < 0.00001) of calcium. These data are significant in that they document lysosomal enzymuria in Nigerian children with severe PEM and point to the potential diagnostic utility of the urinary beta-galactosidase determination for assessing renal function in children with this disorder.
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PMID:Lysosomal enzymuria in protein energy malnutrition. 948 33

Alginate-chitosan core-shell microcapsules were prepared in order to develop a biocompatible matrix for enzyme immobilization, where the protein is retained either in a liquid or solid core and the shell allows permeability control over substrates and products. The permeability coefficients of different molecular weight compounds (vitamin B2, vitamin B12, and myoglobin) were determined through sodium tripolyphosphate (Na-TPP)-crosslinked chitosan membrane. The microcapsule core was formed by crosslinking sodium alginate with either calcium or barium ions. The crosslinked alginate core was uniformly coated with a chitosan layer and crosslinked with Na-TPP. In the case of calcium alginate, the phosphate ions of Na-TPP were able to extract the calcium ions from alginate and liquefy the core. A model enzyme, beta-galactosidase, was immobilized in the alginate core and the catalytic activity was measured with o-nitrophenyl-beta-D-galactopyranoside (ONPG). Change in the activity of free and immobilized enzyme was determined at three different temperatures. Na-TPP crosslinked chitosan membranes were found to be permeable to solutes of up to 17,000Da molecular weight. The enzyme loading efficiency was higher in the barium alginate core (100%) as compared to the calcium alginate core (60%). The rate of ONPG conversion to o-nitrophenol was faster in the case of calcium alginate-chitosan microcapsules as compared to barium alginate-chitosan microcapsules. Barium alginate-chitosan microcapsules, however, did improve the stability of the enzyme at 37 degrees C relative to calcium alginate-chitosan microcapsules or free enzyme. This study illustrates a new method of enzyme immobilization for biotechnology applications using liquid or solid core and shell microcapsule technology.
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PMID:Enzyme immobilization in novel alginate-chitosan core-shell microcapsules. 1473 58


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