Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.1 (alkaline phosphatase)
 47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of activation of alkaline phosphatase (EC 3.1.3.1) from pig kidney by Mg(2+) ions was investigated with the aid of kinetic measurements. Mg(2+) ions are essential for enzyme activity. The following model (Scheme 1 of the text) for the reaction of enzyme, substrate and Mg(2+) ions was derived: [Formula: see text] The binding of the substrate to the enzyme is independent of the binding of the activator, and vice versa. Mg(2+) must therefore play a part in the substrate decomposition. It is not possible to determine whether the Mg(2+) ions are involved directly in the catalytic process, or whether they act as regulatory effectors. Because of the strong affinity existing between the alkaline phosphatase and Mg(2+), it is necessary to adjust the metal-ion concentration with the aid of a metal buffer. In the Appendix the necessary equations are derived for calculating the concentration of free metal ions in a system with several different metal ions. A FORTRAN IV program for solving these equations and for graphic presentation of the results has been deposited as Supplementary Publication SUP 50030 at the British Library (Lending Division) (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS 23 7 BQ, U.K., from whom copies may be obtained on the terms indicated in Biochem. J. (1973), 131, 5.
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PMID:Kinetics of alkaline phosphatase from pig kidney. Mechanism of activation by magnesium ions. 445 3

Liver and activation-regulated chemokine (LARC) is a recently identified CC chemokine that is expressed mainly in the liver. LARC functions as a selective chemoattractant for lymphocytes that express a class of receptors specifically binding to LARC with high affinity. To identifiy the receptor for LARC, we examined LARC-induced calcium mobilization in cells stably expressing five CC chemokine receptors (CCR1-CCR5) and five orphan seven-transmembrane receptors. LARC specifically induced calcium flux in K562 cells as well as 293/EBNA-1 cells stably expressing an orphan receptor GPR-CY4. LARC induced migration in 293/EBNA-1 cells stably expressing GPR-CY4 with a bi-modal dose-response curve. LARC fused with secreted alkaline phosphatase (LARC-SEAP) bound specifically to Raji cells stably expressing GPR-CY4 with a Kd of 0.9 nM. Only LARC but not five other CC chemokines (MCP-1, RANTES, MIP-1alpha, MIP-1beta, and TARC) competed with LARC-SEAP for binding to GPR-CY4. By Northern blot analysis, GPR-CY4 mRNA was expressed mainly in spleen, lymph nodes, Appendix, and fetal liver among various human tissues. Among various leukocyte subsets, GPR-CY4 mRNA was detected in lymphocytes (CD4(+) and CD8(+) T cells and B cells) but not in natural killer cells, monocytes, or granulocytes. Expression of GPR-CY4 mRNA in CD4(+) and CD8(+) T cells was strongly up-regulated by IL-2. Taken together, GPR-CY4 is the specific receptor for LARC expressed selectively on lymphocytes, and LARC is a unique functional ligand for GPR-CY4. We propose GPR-CY4 to be designated as CCR6.
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PMID:Identification of CCR6, the specific receptor for a novel lymphocyte-directed CC chemokine LARC. 916 59

By searching the Expressed Sequence Tag (EST) data base, we identified partial cDNA sequences potentially encoding a novel human CC chemokine. We determined the entire cDNA sequence which encodes a highly basic polypeptide of 134 amino acids total with a putative signal peptide of 23 amino acids. The predicted mature protein of 111 amino acids has the four canonical cysteine residues and shows 21-33% identity to other human CC chemokines, but has a unique carboxyl-terminal extension of about 30 amino acids which contains two extra cysteine residues. The mRNA was expressed strongly in tissues such as the lymph nodes, Appendix, and spleen. The recombinant protein, which was produced by the baculovirus system and purified to homogeneity, was a highly efficient chemoattractant for certain human T cell lines and a highly potent one for freshly isolated peripheral blood lymphocytes and cultured normal T cells expanded by phytohemagglutinin and interleukin 2. Unlike most other CC chemokines, however, this novel chemokine was not chemotactic for monocytes or neutrophils, suggesting that it is specific for lymphocytes. From these results, we designated this novel CC chemokine as SLC from secondary lymphoid-tissue chemokine. SLC fused with the secreted form of alkaline phosphatase (SLC-SEAP) was used to characterize the SLC receptor. Binding of SLC-SEAP to freshly isolated lymphocytes was blocked by SLC (IC50, 0.12 nM) but not by any other CC chemokine so far tested, suggesting that resting lymphocytes express a class of receptors highly specific for SLC. By using somatic cell hybrids, radiation hybrids, and selected yeast and bacterial artificial chromosome clones, we mapped the SLC gene (SCYA21) at chromosome 9p13 and between chromosomal markers, D9S1978(WI-8765) and AFM326vd1, where the gene for another novel CC chemokine termed ELC from EBI1-ligand chemokine (SCYA19) also exists. Collectively, SLC is a novel CC chemokine specific for lymphocytes and, together with ELC, constitutes a new group of chemokines localized at chromosome 9p13.
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PMID:Molecular cloning of a novel human CC chemokine secondary lymphoid-tissue chemokine that is a potent chemoattractant for lymphocytes and mapped to chromosome 9p13. 923 55

To determine initial velocities of enzyme catalyzed reactions without theoretical errors it is necessary to consider the use of the integrated Michaelis-Menten equation. When the reaction product is an inhibitor, this approach is particularly important. Nevertheless, kinetic studies usually involved the evaluation of other inhibitors beyond the reaction product. The occurrence of these situations emphasizes the importance of extending the integrated Michaelis-Menten equation, assuming the simultaneous presence of more than one inhibitor because reaction product is always present. This methodology is illustrated with the reaction catalyzed by alkaline phosphatase inhibited by phosphate (reaction product, inhibitor 1) and urea (inhibitor 2). The approach is explained in a step by step manner using an Excel spreadsheet (available as a template in Appendix). Curve fitting by nonlinear regression was performed with the Solver add-in (Microsoft Office Excel). Discrimination of the kinetic models was carried out based on Akaike information criterion. This work presents a methodology that can be used to develop an automated process, to discriminate in real time the inhibition type and kinetic constants as data (product vs. time) are achieved by the spectrophotometer.
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PMID:Enzyme inhibition studies by integrated Michaelis-Menten equation considering simultaneous presence of two inhibitors when one of them is a reaction product. 2677 32