scholarly journals A kinetic study of the interactions between amino acids and monosaccharides at the intestinal brush-border membrane.

1979 ◽  
Vol 295 (1) ◽  
pp. 457-475 ◽  
Author(s):  
F Alvarado ◽  
J W Robinson
Keyword(s):  
Amino Acids ◽  
Kinetic Study ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border

Role of rat intestinal brush-border membrane angiotensin-converting enzyme in dietary protein digestion

1987 ◽  
Vol 253 (6) ◽  
pp. G781-G786 ◽  
Author(s):  
M. Yoshioka ◽  
R. H. Erickson ◽  
J. F. Woodley ◽  
R. Gulli ◽  
D. Guan ◽  
...  
Keyword(s):  
Amino Acids ◽  
Angiotensin Converting Enzyme ◽  
Brush Border ◽  
Dietary Protein ◽  
Brush Border Membrane ◽  
Biologically Active ◽  
Converting Enzyme ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border

The role of rat intestinal angiotensin-converting enzyme (ACE; E.C 3.4.15.1) in the digestion and absorption of dietary protein was investigated. Enzyme activity was associated with the brush-border membrane fraction, with the highest activity in the proximal to midregion of the small intestine. Preliminary enzyme characterization studies were carried out using purified brush-border membrane preparations. When a variety of N-blocked synthetic peptides were used as potential substrates for ACE, activity was highest with those containing proline at the carboxy terminal position. The hydrolytic rates observed with these prolyl peptides were comparable to those observed when major digestive peptidases of the brush-border membrane such as aminopeptidase N and dipeptidyl aminopeptidase IV were assayed. When isolated rat jejunum was perfused in vivo with solutions of Bz-Gly-Ala-Pro, the dipeptide Ala-Pro was the main hydrolytic product detected in the perfusates. Absorption rates of the constituent amino acids, alanine and proline, depended on the concentration of peptide perfused. Captopril, an active site specific ACE inhibitor, significantly inhibited hydrolysis and absorption of constituent amino acids from Bz-Gly-Ala-Pro. These results show that intestinal brush-border membrane ACE functions as a digestive peptidase in addition to its role as a regulator of biologically active peptides in other tissues.

Divalent cations and vitamin B12 uptake by intestinal brush-border membrane vesicles

1980 ◽  
Vol 239 (6) ◽  
pp. G452-G456
Author(s):  
R. C. Beesley ◽  
C. D. Bacheller
Keyword(s):  
Vitamin B12 ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Divalent Cations ◽  
Intrinsic Factor ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Tetraacetic Acid ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border

Brush-border membrane vesicles from hamster intestine were employed to investigate uptake (binding) of vitamin B12 (B12). Ileal vesicles took up 25 times more B12 than did jejunal vesicles. Uptake of B12 by ileal vesicles was dependent on intrinsic factor (IF) and required Ca2+. Increasing the Ca2+ concentration caused an increase in uptake of B12 reaching a maximum at approximately 8 mM Ca2+. At high Ca2+ concentrations, 6–8 mM, Mg2+ had little effect on uptake of B12. At low Ca2+ concentrations, up to 2 mM, Mg2+ stimulated B12 uptake. Mg2+, Mn2+, and, to a lesser extent, Sr2+ stimulated Ca2+-dependent B12 uptake, but Zn2+, Ba2+, Na+, K+, and La3+ did not. B12 was apparently not metabolized and was bound as IF-B12 complex, which could be removed with (ethylenedinitrilo)tetraacetic acid (EDTA). Our results suggest that two types of divalent cation reactive sites are involved in binding of IF-B12. One is Ca2+ specific. The other is less specific reacting with Mg2+, Mn2+, Sr2+, and perhaps Ca2+ itself, thereby stimulating Ca2+-dependent binding of IF-B12 to its ileal receptor.

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