Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0002895 (sickle cell disease)
 11,747 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A somewhat simplified modification of a previously described method for the measurement of red cell membrane phosphorylation by ATP has been devised. Phosphorylation of membranes was linear with time for only 5-10 min, and linearity with membrane concentration was observed only when assays were limited to short incubation times. Protein kinase activity of hereditary spherocytosis (HS) membranes was found to be normal. However, the average phosphorylation after 60 min incubation was less in HS membranes than in normal membranes. Findings similar to those in HS membranes were observed in sickle cell disease. The Km of red cell protein kinase for ATP is approximately 10(-5) M. Membrane phosphate binding sites are not saturated in either HS or normal membranes after 1 hr incubation with ATP. Approximately 27% of phosphorylating activity is lost after 1 hr incubation at 37 degrees C. GTP is a very inefficient phosphate donor. Under the conditions of measurement employed, the enzyme is slightly stimulated by 1 muM cAMP, but is not stimulated by 1 muM cGMP. Dephosphorylation of red cell membranes after labeling occurs at a similar rate in HS as in normal membranes. Although a mild abnormally in membrane phosphorylation is observed in HS, this could not be demonstrated to be due to a decrease in protein kinase activity or in alterations of its kinetic properties. The abnormally seen is not specific for HS.
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PMID:Human red cells protein kinase in normal subjects and patients with hereditary spherocytosis, sickle cell disease, and autoimmune hemolytic anemia. 18 65

Protein kinase activities and membrane autophosphorylation reactions of normal and abnormal human erythrocytes were analyzed. Erythrocytes from patients with high reticulocytosis due to sickle cell anemia and other disorders (n = 13) exhibited elevated activities of total and membrane-bound cAMP-independent casein kinase and cAMP-stimulated histone kinase. Relative to normal controls (n = 10), the average total activities in these abnormal cells were increased 50% and 81%, respectively. The casein and histone kinase activities of normal and abnormal erythrocytes declined significantly with increasing age and buoyant density in Stractan density gradients. Casein kinase activity was highly correlated (r = 0.88; n = 23) with the percentage of reticulocytes in the fraction, consistent with either a progressive loss of activity in mature erythrocytes or an abrupt decline during reticulocyte maturation. The cAMP-independent and cAMP-stimulated autophosphorylation activities of isolated membranes also declined with increasing erythrocyte age. On average, the initial rate of spectrin labeling was 36% lower in ghosts from Stractan gradient bottom fractions, relative to ghosts from top fractions similarly incubated with gamma-32P-ATP. Incorporation into the "band 4.5 zone" (primarily labeling bands 4.8 and 4.9, mol wt 47,800 and 44,600) was also age-dependent. In membranes of unfractionated sickle cells, spectrin autophosphorylation was within normal limits, while 4.5 zone autophosphorylation was increased. Membranes from high reticulocytosis controls (vitamin B-12 deficiency) exhibited similar autophosphorylation patterns, suggesting that the altered autophosphorylation pattern of sickle cell membranes may be attributed to the predominance of very young cells.
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PMID:Protein kinases and membrane protein phosphorylation in normal and abnormal human erythrocytes: variation related to mean cell age. 683 Oct 46