scholarly journals The hydrolysis of nicotinamide adenine nucleotide by brush border membranes of rat intestine

1982 ◽  
Vol 204 (1) ◽  
pp. 203-207 ◽  
Author(s):  
C L Baum ◽  
J Selhub ◽  
I H Rosenberg
Keyword(s):  
High Pressure ◽  
Enzyme Activity ◽  
Brush Border ◽  
Membrane Fraction ◽  
Brush Border Membrane ◽  
Adenine Nucleotide ◽  
Rat Intestine ◽  
Nicotinamide Riboside ◽  
Nicotinamide Mononucleotide ◽  
Hydrolysis Of

The hydrolysis of NAD by rat intestine was studied to determine the subcellular site of this hydrolysis and to identify the niacin-containing products that are formed. Using [nicotinamide-14C]NAD as substrate, and high pressure liquid chromatography for identification and quantification of products, the present study demonstrates two independent reactions for the hydrolysis of NAD; one that forms nicotinamide through hydrolysis of the ribosyl-pyridinium bond and one that forms nicotinamide mononucleotide through the hydrolysis of the pyrophosphate bond. The nicotinamide mononucleotide is subsequently dephosphorylated to nicotinamide riboside. Enzymes which release nicotinamide mononucleotide and nicotinamide riboside are associated with the brush border membrane as determined by analysis of fractionated intestinal homogenates. The enzyme activity which releases nicotinamide from NAD is associated with the brush border membrane fraction and also with a second cellular particulate fraction. Between pH5 and pH6 NAD is hydrolysed principally to nicotinamide. At pH 7.0 rates of nicotinamide and nicotinamide mononucleotide formation are the same. Above pH 7.0 the formation of nicotinamide mononucleotide is preferred.

Sugar hydrolases of the infant rat intestine and their arrangement on the brush border membrane

1979 ◽  
Vol 554 (1) ◽  
pp. 234-248 ◽  
Author(s):  
Kenneth K. Tsuboi ◽  
Steven M. Schwartz ◽  
Peter H. Burrill ◽  
Linda K. Kwong ◽  
Philip Sunshine
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Rat Intestine ◽  
Infant Rat

Adaptive regulation of brush-border amino acid transport in a chronic excluded jejunal limb

1991 ◽  
Vol 261 (1) ◽  
pp. G22-G27
Author(s):  
R. M. Salloum ◽  
B. R. Stevens ◽  
W. W. Souba
Keyword(s):  
Enzyme Activity ◽  
Brush Border ◽  
Permeability Coefficient ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Marker Enzymes ◽  
Acid Transport ◽  
Glutamine Transport ◽  
Intestinal Section ◽  
Glutaminase Activity

We examined the alterations in brush-border glutamine transport that occurred in a surgically defunctionalized jejunal limb excluded from mucosal food contact. Dogs were surgically prepared with Roux-en-Y gastrojejunostomies to permit same-intestine comparisons of glutamine transport and glutaminase activity in jejunal segments that were in incontinuity or excluded for a 6-mo period. Transport of glutamine, alanine, and glucose was measured in brush-border membrane vesicles prepared from each intestinal section; membrane marker enzymes were enriched to the same degree in incontinuity and excluded portions. The Na(+)-dependent glutamine cotransport apparent Km was the same in the excluded (779 +/- 63 microM) and incontinuity (873 +/- 105 microM) limbs. However, the Jmax for Na(+)-independent glutamine transport in the incontinuity jejunum (158.7 +/- 15.7 pmol.mg protein-1.s-1) was double that in the excluded limb (71.2 +/- 4.6 pmol.mg protein-1.s-1). Na(+)-dependent carrier-mediated glutamine transport rates were lower than the Na(+)-dependent system, but Na(+)-independent kinetic parameters were not significantly different in incontinuity vs. excluded limbs (Jmax 7.9 +/- 0.6 pmol.mg protein-1.s-1; Km 140 +/- 20 microM). Similarly, the passive diffusion permeability coefficient was the same for both excluded and incontinuity jejunal limbs (22.7 +/- 0.9 nl.mg protein-1.s-1). Mucosal glutaminase enzyme activity was increased by 28% in the incontinuity limb (4.32 +/- 0.21 vs. 3.36 +/- 0.35 mumol.mg protein-1.h-1; P less than 0.02). Transport rates of alanine and glucose were also diminished in the excluded limb (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals A comparison of the active site of maltase-glucoamylase from the brush border of rabbit small intestine and kidney by chemical modification studies

1991 ◽  
Vol 274 (2) ◽  
pp. 349-354 ◽  
Author(s):  
B Pereira ◽  
S Sivakami
Keyword(s):  
Chemical Modification ◽  
Brush Border ◽  
Active Site ◽  
Brush Border Membrane ◽  
Kidney Enzyme ◽  
Rabbit Intestine ◽  
Rabbit Small Intestine ◽  
Intestinal Enzyme ◽  
The One ◽  
Hydrolysis Of

The neutral maltase-glucoamylase complex has been purified to homogeneity from the brush-border membrane of rabbit intestine and kidney. Chemical modification of the amino acid side chains was carried out on the purified enzymes. Studies on the kidney enzyme revealed that tryptophan, histidine and cysteine were essential for both maltase and glucoamylase activities, whereas tryptophan, histidine and lysine were essential for the maltase and glucoamylase activities of the intestinal enzyme. Though there was no difference in the amino acids essential for the hydrolysis of maltose and starch by any one enzyme, starch hydrolysis seems to require two histidine residues instead of the one which is required for maltose hydrolysis. This appears to be true for both the intestinal and kidney enzymes.

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