Mechanism of kinase

Figure 1. a) Structural isomers of 3iY-bidentate M(III)ATP and a,3-bidentate M(III)ADP complexes b) Proposed mechanisms of kinases. 

Figure 15 Acyl adenosine phosphate probes for the selective labeling of kinases at their ATP-binding site, (a) Probes were designed on the basis of ATP or ADP. (b) Mechanism of kinase labeling. A conserved active site lysine attacks the acyl phosphate resulting in acylation of the enzyme by a biotin tag.

The Ser/Thr- and Tyr-specific protein kinases share many common features. The catalytic mechanism, structural properties and mechanisms of kinase control are very similar for the two kinase classes. In the following, the main properties of both classes will therefore be presented together (reviews Johnson et al., 1998 Engh and Bosse-meyer, 2001). ... 

Activation segment exchange a common mechanism of kinase autophosphorylation Trends Biochem. Sci., 32, 351-356. 

The kinetic mechanism of kinase inhibitors often has been investigated by varying the concentration of ATP. The dependence upon concentration of phosphoacceptor substrate is rarely reported. ATP-dependence allows comparison across all kinases as it is the universal phosphate donor, and it gives useful information, because the most inhibitors use the purine site. 

M. Huse, M.N. Holford, J. Kuriyan, T.W. Muir, Semisynthesis of hyperphosphorylated type I TGF/3 receptor addressing the mechanism of kinase activation, J. Am. Chem. Soc. 

Left side of Fig. 4 shows a ribbon model of the catalytic (C-) subunit of the mammalian cAMP-dependent protein kinase. This was the first protein kinase whose structure was determined [35]. Figure 4 includes also a ribbon model of the peptide substrate, and ATP (stick representation) with two manganese ions (CPK representation). All kinetic evidence is consistent with a preferred ordered mechanism of catalysis with ATP binding proceeding substrate binding. 

The antiviral mechanism of action of acyclovir has been reviewed (72). Acyclovir is converted to the monophosphate in herpes vims-infected cells (but only to a limited extent in uninfected cells) by viral-induced thymidine kinase. It is then further phosphorylated by host cell guanosine monophosphate (GMP) kinase to acyclovir diphosphate [66341 -17-1], which in turn is phosphorylated to the triphosphate by unidentified cellular en2ymes. Acyclovir triphosphate [66341 -18-2] inhibits HSV-1 viral DNA polymerase but not cellular DNA polymerase. As a result, acyclovir is 300 to 3000 times more toxic to herpes vimses in an HSV-infected cell than to the cell itself. Studies have shown that a once-daily dose of acyclovir is effective in prevention of recurrent HSV-2 genital herpes (1). HCMV, on the other hand, is relatively uninhibited by acyclovir. 

A/-(2,3-Epoxypropyl)-A/-amidinoglycine [70363-44-9] (21) was shown to be an affinity label of creatine kinase. Its mechanism of covalent bond formation is outlined as follows ... 

Zhou G, Myers R, Li Y et al (2001) Role of AMP-activated protein kinase in mechanism of metformin action. J Clin Invest 108 1167-1174... 

Concanavalin A is a plant lectin from the jack bean (Canavalia ensiformis) which binds with high affinity to mannose residues of glycoproteins. Concanavalin A is known to stimulate the tyrosine kinase activity of the INSR (3-subunit with consecutive activation of kinases downstream the insulin receptor (IRS, PI 3-kinase). It is believed that Concanavalin A stimulates the activation and autophosphorylation of the INSR kinase through aggregation of the receptor, although the precise mechanism of action is unclear. 

Kinase Inhibitors Mechanism of Action Biological Consequences... 

Growth inhibition by TGF- 3, associated with inhibition of c-myc, cdks, reduction in cyclin D1 levels, and inhibition of cdk-4-associated Rb kinase activity, as well as induction of cdk inhibitors pi5 and p27, has been noted in intestinal epithelial cells. Loss of responsiveness to growth inhibition from TGF- 3 occurs in many cell types including breast, colorectal carcinoma, and pancreatic carcinoma cells. Mutational inactivation of T 3RH represents one mechanism of this process, which in many cases, leads to the development of gastrointestinal cancer. Thirteen percent of colorectal carcinomas are thought to be associated with a replication error (RER) or microsatellite instability phenotype. Subsequent inactivation of T 3RII and... 

Vasodilators are a group of dtugs, which relax the smooth muscle cells of the blood vessels and lead to an increased local tissue blood flow, a reduced arterial pressure and a reduced central venous pressure. Vasodilators reduce the cardiac pre-load as well as after-load and thereby reduce cardiac work. They are used in a variety of conditions including hypertension, cardiac failure and treatment/prevention of angina pectoris. Major groups are Ca2+-channel blockers (e.g. dihydropyridines), NO-donators (e.g. organic nitrates), K+-channel openers (minoxidil), phosphodiesterase inhibitors (e.g. sildenafil), Rho-kinase inhibitors (e.g. Y27632) or substances with unknown mechanism of action (e.g. hydralazine). Inhibitors of the... 

Figure 2. Mechanism of PDH. The three different subunits of the PDH complex in the mitochondrial matrix (E, pyruvate decarboxylase E2, dihydrolipoamide acyltrans-ferase Ej, dihydrolipoamide dehydrogenase) catalyze the oxidative decarboxylation of pyruvate to acetyl-CoA and CO2. E, decarboxylates pyruvate and transfers the acetyl-group to lipoamide. Lipoamide is linked to the group of a lysine residue to E2 to form a flexible chain which rotates between the active sites of E, E2, and E3. E2 then transfers the acetyl-group from lipoamide to CoASH leaving the lipoamide in the reduced form. This in turn is oxidized by E3, which is an NAD-dependent (low potential) flavoprotein, completing the catalytic cycle. PDH activity is controlled in two ways by product inhibition by NADH and acetyl-CoA formed from pyruvate (or by P-oxidation), and by inactivation by phosphorylation of Ej by a specific ATP-de-pendent protein kinase associated with the complex, or activation by dephosphorylation by a specific phosphoprotein phosphatase. The phosphatase is activated by increases in the concentration of Ca in the matrix. The combination of insulin with its cell surface receptor activates PDH by activating the phosphatase by an unknown mechanism.

Of the several kinase activities which are important in smooth muscle, myosin light chain kinase, MLCK, is the one responsible for activation of the actin-myosin system to in vivo levels. MLCK is present in the other nonmuscle cell types which have the actin-myosin contractile system and all of these are probably activated in a manner similar to smooth muscle rather than by way of the Ca -troponin mechanism of striated muscle. MLCK from smooth muscle is about 130 kDa and is rather variable in shape. It is present in smooth muscle in 1-4 pM concentrations and binds with an equally high affinity to both myosin and actin. Thus, most MLCK molecules are bound to actin. Myosin light chain serine-19 is the primary target of smooth muscle myosin light chain kinase. 

TBT and TFT are membrane-active molecules, and their mechanism of action appears to be strongly dependent on organotin(IV) lipophilicity. They function as ionophores and produce hemolysis, release Ca(II) from sarcoplasmic reticulum, alter phosphatodylseiine-induced histamine release, alter mitochondrial membrane permeability and perturb membrane enzymes. Organotin(IV) compounds have been shown to affect cell signaling they activate protein kinase and increase free arachidonic acid through the activation of phospholipase... 

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