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Multiple pathways for L-methionine transport in brush-border membrane vesicles from chicken jejunum.
J Physiol. 1998 Jun 01; 509 (Pt 2):527-39.JP

Abstract

1. The intestinal transport of L-methionine has been investigated in brush-border membrane vesicles isolated from the jejunum of 6-week-old chickens. L-Methionine influx is mediated by passive diffusion and by Na+-dependent and Na+-independent carrier-mediated mechanisms. 2. In the absence of Na+, cis-inhibition experiments with neutral and cationic amino acids indicate that two transport components are involved in L-methionine influx: one sensitive to L-lysine and the other sensitive to 2-aminobicyclo[2.2. 1]heptane-2-carboxylic acid (BCH). The L-lysine-sensitive flux is strongly inhibited by L-phenylalanine and can be broken down into two pathways, one sensitive to N-ethylmaleimide (NEM) and the other to L-glutamine and L-cystine. 3. The kinetics of L-methionine influx in Na+-free conditions is described by a model involving three transport systems, here called a, b and c: systems a and b are able to interact with cationic amino acids but differ in their kinetic characteristics (system a: Km = 2.2 +/- 0.3 microM and Vmax = 0.13 +/- 0.005 pmol (mg protein)-1 (2 s)-1; system b: Km = 3.0 +/- 0.3 mM and Vmax = 465 +/- 4.3 pmol (mg protein)-1 (2 s)-1); system c is specific for neutral amino acids, has a Km of 1.29 +/- 0.08 mM and a Vmax of 229 +/- 5.0 pmol (mg protein)-1 (2 s)-1 and is sensitive to BCH inhibition. 4. The Na+-dependent component can be inhibited by BCH and L-phenylalanine but cannot interact either with cationic amino acids or with alpha-(methylamino)isobutyrate (MeAIB). 5. The kinetic analysis of L-methionine influx under a Na+ gradient confirms the activity of the above described transport systems a and b. System a is not affected by the presence of Na+ while system b shows a 3-fold decrease in the Michaelis constant and a 1.4-fold increase in Vmax. In the presence of Na+, the BCH-sensitive component can be subdivided into two pathways: one corresponds to system c and the other is Na+ dependent and has a Km of 0.64 +/- 0. 013 mM and a Vmax of 391 +/- 2.3 pmol (mg protein)-1 (2 s)-1. 6. It is concluded that L-methionine is transported in the chicken jejunum by four transport systems, one with functional characteristics similar to those of system bo, + (system a); a second (system b) similar to system y+, which we suggest naming y+m to account for its high Vmax for L-methionine transport in the absence of Na+; a third (system c) which is Na+ independent and has similar properties to system L; and a fourth showing Na+ dependence and tentatively identified with system B.

Authors+Show Affiliations

Departament de Fisiologia-Divisio IV, Facultat de Farmàcia, Universitat de Barcelona, E-08028 Barcelona, Spain.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

9575301

Citation

Soriano-García, J F., et al. "Multiple Pathways for L-methionine Transport in Brush-border Membrane Vesicles From Chicken Jejunum." The Journal of Physiology, vol. 509 (Pt 2), 1998, pp. 527-39.
Soriano-García JF, Torras-Llort M, Ferrer R, et al. Multiple pathways for L-methionine transport in brush-border membrane vesicles from chicken jejunum. J Physiol. 1998;509 (Pt 2):527-39.
Soriano-García, J. F., Torras-Llort, M., Ferrer, R., & Moreto, M. (1998). Multiple pathways for L-methionine transport in brush-border membrane vesicles from chicken jejunum. The Journal of Physiology, 509 (Pt 2), 527-39.
Soriano-García JF, et al. Multiple Pathways for L-methionine Transport in Brush-border Membrane Vesicles From Chicken Jejunum. J Physiol. 1998 Jun 1;509 (Pt 2):527-39. PubMed PMID: 9575301.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Multiple pathways for L-methionine transport in brush-border membrane vesicles from chicken jejunum. AU - Soriano-García,J F, AU - Torras-Llort,M, AU - Ferrer,R, AU - Moreto,M, PY - 1998/5/12/pubmed PY - 1998/5/12/medline PY - 1998/5/12/entrez SP - 527 EP - 39 JF - The Journal of physiology JO - J Physiol VL - 509 (Pt 2) N2 - 1. The intestinal transport of L-methionine has been investigated in brush-border membrane vesicles isolated from the jejunum of 6-week-old chickens. L-Methionine influx is mediated by passive diffusion and by Na+-dependent and Na+-independent carrier-mediated mechanisms. 2. In the absence of Na+, cis-inhibition experiments with neutral and cationic amino acids indicate that two transport components are involved in L-methionine influx: one sensitive to L-lysine and the other sensitive to 2-aminobicyclo[2.2. 1]heptane-2-carboxylic acid (BCH). The L-lysine-sensitive flux is strongly inhibited by L-phenylalanine and can be broken down into two pathways, one sensitive to N-ethylmaleimide (NEM) and the other to L-glutamine and L-cystine. 3. The kinetics of L-methionine influx in Na+-free conditions is described by a model involving three transport systems, here called a, b and c: systems a and b are able to interact with cationic amino acids but differ in their kinetic characteristics (system a: Km = 2.2 +/- 0.3 microM and Vmax = 0.13 +/- 0.005 pmol (mg protein)-1 (2 s)-1; system b: Km = 3.0 +/- 0.3 mM and Vmax = 465 +/- 4.3 pmol (mg protein)-1 (2 s)-1); system c is specific for neutral amino acids, has a Km of 1.29 +/- 0.08 mM and a Vmax of 229 +/- 5.0 pmol (mg protein)-1 (2 s)-1 and is sensitive to BCH inhibition. 4. The Na+-dependent component can be inhibited by BCH and L-phenylalanine but cannot interact either with cationic amino acids or with alpha-(methylamino)isobutyrate (MeAIB). 5. The kinetic analysis of L-methionine influx under a Na+ gradient confirms the activity of the above described transport systems a and b. System a is not affected by the presence of Na+ while system b shows a 3-fold decrease in the Michaelis constant and a 1.4-fold increase in Vmax. In the presence of Na+, the BCH-sensitive component can be subdivided into two pathways: one corresponds to system c and the other is Na+ dependent and has a Km of 0.64 +/- 0. 013 mM and a Vmax of 391 +/- 2.3 pmol (mg protein)-1 (2 s)-1. 6. It is concluded that L-methionine is transported in the chicken jejunum by four transport systems, one with functional characteristics similar to those of system bo, + (system a); a second (system b) similar to system y+, which we suggest naming y+m to account for its high Vmax for L-methionine transport in the absence of Na+; a third (system c) which is Na+ independent and has similar properties to system L; and a fourth showing Na+ dependence and tentatively identified with system B. SN - 0022-3751 UR - https://www.unboundmedicine.com/medline/citation/9575301/Multiple_pathways_for_L_methionine_transport_in_brush_border_membrane_vesicles_from_chicken_jejunum_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0022-3751&date=1998&volume=509&spage=527 DB - PRIME DP - Unbound Medicine ER -