Specific lysosomal transport of small neutral amino acids
Studies of amino acid exodus from lysosomes have allowed us previously to describe transport systems specific for cystine and another for cationic amino acids in fibroblast lysosomes. They are now able to study amino acid uptake into highly purified fibroblast lysosomes obtained by separating crude granular fraction on gradients formed by centrifugation in 35% isoosmotic Percoll solutions. Analog inhibition and saturation studies indicate that L-(/sup 14/C)proline (50 ..mu..M) uptake by fibroblast lysosomes at 37/sup 0/C in 50 mM citrate/tris pH 7.0 buffer containing 0.25 M sucrose is mediated by two transport systems, one largely specific for L-proline and the other for which transport is shared with small neutral amino acids such as alanine, serine and threonine. At 7 mM, L-proline inhibits L-(/sup 14/C)proline uptake almost completely, whereas ala, ser, val, thr, gly, N-methylalanine and sarcosine inhibit proline uptake by 50-65%. The system shared by alanine, serine and threonine is further characterized by these amino acids strongly inhibiting the uptakes of each other. Lysosomal proline transport is selective for the L-isomer of the amino acid, and is scarcely inhibited by 7 mM arg, glu, asp, leu, phe, his, met, (methylamino) isobutyrate, betaine or N,N-dimethylglycine. Cis or trans-4-hydroxy-L-proline inhibit proline uptake only slightly. In sharp contrast to the fibroblast plasma membrane in which Na/sup +/ is required for most proline and alanine transport, lysosomal uptake of these amino acids occurs independently of Na/sup +/.
- Research Organization:
- Univ. of Michigan Medical School, Ann Arbor
- OSTI ID:
- 7108616
- Report Number(s):
- CONF-8606151-; TRN: 86-039062
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:7; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
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AMINO ACIDS
MEMBRANE TRANSPORT
ALANINES
CARBON 14 COMPOUNDS
CENTRIFUGATION
FIBROBLASTS
GLYCINE
INHIBITION
LYSOSOMES
PROLINE
SERINE
THREONINE
TRACER TECHNIQUES
AMINES
ANIMAL CELLS
AZOLES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CONNECTIVE TISSUE CELLS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOIDS
PYRROLES
PYRROLIDINES
SEPARATION PROCESSES
SOMATIC CELLS
550201* - Biochemistry- Tracer Techniques