Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human myristoyl-CoA:protein N-myristoyltransferase (hNmt) catalyzes the transfer of myristate from CoA to the amino-terminal Gly residue of a number of cellular proteins involved in signal transduction pathways, to structural and nonstructural proteins encoded by retroviruses, hepadnaviruses, picornaviruses, and reoviruses, as well as to several transforming tyrosine kinases. hNmt has been purified 230-fold from an erythroleukemia cell line. The monomeric enzyme has no associated methionyl aminopeptidase activity. To determine the enzyme's kinetic mechanism, we examined the effect of covariation of subsaturating concentrations of myristoyl-CoA and peptide substrate on initial velocity. Double-reciprocal plots excluded a double displacement (ping-pong) mechanism. Product inhibition studies indicated that CoA was a noncompetitive inhibitor against myristoyl-CoA and a mixed-type inhibitor against peptide substrates. Together these results are consistent with a sequential ordered mechanism where, in a typical catalytic cycle, myristoyl-CoA binds to apoenzyme before peptide followed by release of the CoA and then myristoylpeptide products. This kinetic mechanism is identical to that described for Saccharomyces cerevisiae N-myristoyl-transferase (Nmt1p) and emphasizes the impact that regulation of myristoyl-CoA pool size and accessibility may have in modulating protein N-myristoylation in these two species. Comparative studies of the peptide substrate specificities of hNmt and Nmt1p using a panel of 12 octapeptides revealed distinct differences in their tolerance for amino acid substitutions at positions 3, 4, 7, and 8 of parental peptides derived from the amino-terminal sequences of known N-myristoyl-proteins. This finding contrasts with our recent observation that the acyl-CoA substrate specificities of hNmt and Nmt1p are highly conserved and suggests that these differences in peptide recognition provide an opportunity to develop species-specific enzyme inhibitors.
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PMID:A comparative analysis of the kinetic mechanism and peptide substrate specificity of human and Saccharomyces cerevisiae myristoyl-CoA:protein N-myristoyltransferase. 848 23

The role of Ras and MAP kinases (MAPKs) in the regulation of erythroid differentiation was studied using a cell line (SKT6) derived from Friend virus (Anemic strain)-induced murine erythroleukemia. This cell line undergoes differentiation in vitro in response to erythropoietin (EPO) or other chemical inducers such as dimethylsulfoxide (DMSO). When a constitutively active ras mutant (ras12V) was expressed in SKT6 cells, EPO-induced differentiation was inhibited. Conversely, a dominant negative ras mutant (ras17N) induced differentiation even in the absence of EPO, suggesting that the basal Ras activity is essential for the maintenance of the undifferentiated phenotype and proliferative potential in this cell line. Rapid inactivation of ERK was observed after expression of ras17N. Slow but significant inactivation of ERK was also observed during EPO-induced differentiation. Furthermore, overexpression of a constitutively active mutant of ERK-activating kinase (MAPKK) was found to suppress erythroid differentiation, while pharmacological inhibition of MAPKK induced differentiation. These findings suggest that down-regulation of Ras/ERK signaling pathway may be an essential event in EPO-induced erythroid differentiation in this system.
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PMID:Induction of erythroid differentiation by inhibition of Ras/ERK pathway in a friend murine leukemia cell line. 1073 9

Cyclopentenyl cytosine (CPEC) is a carbocyclic cytidine analog inhibitor of CTP synthetase and experimental drug for combination chemotherapy. CPEC treatment (50 nM) depleted intracellular CTP and induced a specific S-phase arrest and erythroid differentiation of human erythroleukemia K562 cells. The equilibrative nucleoside transporters (ENT1, 2) facilitated uptake of CPEC into K562 cells as evidenced by both NBMPR and dipyridamole inhibition of CPEC-mediated CTP depletion and erythroid differentiation. Incubation with the pyridinylimidazole p38 MAPK inhibitors, SB203580 or SB220025, suppressed both the CPEC-induced cell cycle arrest and differentiation of K562 cells. SB203580 also prevented the cell cycle arrest and erythroid differentiation of K562 cells induced by Leflunomide (LEF), a non-nucleoside inhibitor of the de novo pyrimidine pathway, without affecting LEF-induced depletion of pyrimidine pools. Finally, selective knockdown of p38 MAPK by using Smart Pooltrade mark siRNA to p38 MAPK significantly decreased the CPEC-induced differentiation of K562 cells. These results suggest that endogenous activity of p38 MAP kinases may be required for committing K562 cells to cell cycle arrest and erythroid differentiation under conditions of CTP depletion.
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PMID:CPEC induces erythroid differentiation of human myeloid leukemia K562 cells through CTP depletion and p38 MAP kinase. 1538 35