Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sarcolemmal vesicles isolated from human skeletal muscle obtained at surgery showed approximately 14-fold enrichment of sarcolemmal marker enzymes 5'-nucleotidase and K-stimulated phosphatase. [3H]glutamine transport in these vesicles was stereospecific, largely Na dependent, and tolerated Li-for-Na substitution. Glutamine transport was stimulated by an inside negative membrane potential, and 25 mM glutamine stimulated 22Na (0.1 mM) uptake into vesicles by 50%, indicating rheogenic cotransport of Na and glutamine. Alanine transport was Na dependent but did not tolerate Li-for-Na substitution. Transport of L-[3H]glutamine was inhibited by 35-65% with a 20-fold excess of glutamine, asparagine, and alanine; cysteine, alpha-(methylamino)isobutyrate, and 2-amino-2-norborane carboxylic acid had smaller inhibitory effects, although cysteine had an unusually large inhibitory effect on glutamine transport at 1,000-fold excess compared with most other amino acids. Glutamine transport showed sensitivity to pH values < 7.0. Glutamine transport consisted of a Na-dependent and a Na-independent component, both of which appeared saturable. The kinetic characteristics of the Na-dependent component were different in different types of muscles, with half-maximal concentrations (mM) varying from 1.6 +/- 0.4 (tibialis anterior) to 0.56 +/- 0.0.2 (gluteus maximus) and maximal velocity (pmol.mg protein-1.s-1) of 1.3 +/- 0.27 to 5 +/- 1.25 in the same muscles. The results demonstrate both marked similarities and important differences between the principal glutamine transporter in human skeletal muscle and the known system Nm transporter in rat skeletal muscle.
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PMID:Glutamine transport in human skeletal muscle. 833 25

In the human body skeletal muscle is the largest store of glutamine, an important amino-acid in whole body nitrogen balance. Glutamine transport was measured in purified human skeletal muscle sarcolemmal vesicles (HMSV). The activity of sarcolemmal marker enzymes (K(+)-stimulated nitrophenylphosphatate (KpNPPase) and 5'-nucleotidase) was increased approximately 14-fold in the sarcolemmal fraction (SF) compared to the crude muscle homogenate (CH). Glutamine transport in HMSV was Na(+)-dependent (initial rate of 1 muM glutamine in the presence of 0.1 M NaCl = 7 (+/- 1.7) x 10(-3) pmol.mg(-1) protein.s(-1) compared to 1.5 (+/- 0.3) x 10(-3) pmol mg(-1) protein.s(-1) in the presence of 0.1 M Choline Cl). The rate of glutamine uptake into HMSV was increased in the presence of an inside negative membrane potential.
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PMID:Studies of glutamine uptake across human skeletal sarcolemma. 1683 72