CDK-activating Kinase - Catalytic Activity

Catalytic Activity

Cdk activation requires two steps. First, cyclin must bind to the Cdk. In the second step, CAK must phosphorylate the cylin-Cdk complex on the threonine residue 160, which is located in the Cdk activation segment. Since Cdks need to be free of Cdk inhibitor proteins (CKIs) and associated with cyclins in order to be activated, CAK activity is considered to be indirectly regulated by cyclins.

Phosphorylation is generally considered a reversible modification used to change enzyme activity in different conditions. However, activating phosphorylation of Cdk by CAK appears to be an exception to this trend. In fact, CAK activity remains high throughout the cell cycle and is not regulated by any known cell-cycle control mechanism. However compared to normal cells, CAK activity is reduced in quiescent G0 cells and slightly elevated in tumor cells.

In mammals, activating phosphorylation by CAK can only occur once cylin is bound. In budding yeast, activating phosphorylation by CAK can take place before cyclin binding. In both humans and yeast, cyclin binding is the rate limiting step in the activation of Cdk. Therefore, phosphorylation of Cdk by CAK is considered a post-translational modification that is necessary for enzyme activity. Although activating phosphorylation by CAK is not exploited for cell-cycle regulation purposes, it is a highly conserved process because CAK also regulates transcription.

Read more about this topic:  CDK-activating Kinase

Other articles related to "catalytic activity, catalytic, activity":

Proton Exchange Membrane Fuel Cell - Science - Catalyst Research - Increasing Catalytic Activity
... main goal of catalyst design for PEM fuel cells is to increase the catalytic activity of platinum by a factor of four so that only one-fourth as much of the precious metal is ... but recent studies have demonstrated additional ways to make further improvements to catalytic performance ... A second method of increasing the catalytic activity of platinum is to alloy it with other metals ...
Acetolactate Synthase - Catalytic Activity
... are four specific residues that are responsible for catalytic activity in this enzyme ... Residues involved in catalytic activity are bolded ... Catalytic residues are bold TFISRFAPDQPRKGADILVEALERQGVETVFAYPGGASMEIHQALTRSSSIRNVLPRHEQGGVFAAEGYARSSGKPGICIATSGPGATNLVSGLADALLD ...
Sphingomyelin Phosphodiesterase - Neutral Sphingomyelinase - Active Site
... residues Glu-53, Asp-195, and His-296 are known to be essential for activity ... The relative catalytic activities of SMase when metal ions are bound to the active site have been studied for divalent metal ions Co2+, Mn2+, Mg2+, Ca2+, and ... Co2+, Mn2+, and Mg2+ bound to the active site result in high catalytic activity of SMase ...
PTPRT - Tyrosine Phosphatase Activity
... The first catalytic domain of Type R2B RPTPs is considered the active phosphatase domain, whereas the second phosphatase domain is thought to be inactive ... however, result in a reduction of phosphatase activity of PTPrho ... of the second tyrosine phosphatase domain in colorectal cancer cells also reduces PTPrho catalytic activity, again demonstrating that the second phosphatase domain of PTPrho ...
Ammonium Metavanadate - Metallurgy
... Ammonium metavanadate has been mixed with basic copper carbonate to make a new compound with better catalytic activity than the two separate compounds ... In the study by Shaheen and Maksod, catalytic activity of different molar ratios of ammonium metavanadate in comparison with the two original compounds was examined at different calcinations temperatures ... Catalytic activity was measured “using hydrogen peroxide decomposition at 30, 40, and 50°C” for pure and mixed compounds ...

Famous quotes containing the word activity:

    History does nothing; it does not possess immense riches, it does not fight battles. It is men, real, living, who do all this.... It is not “history” which uses men as a means of achieving—as if it were an individual person—its own ends. History is nothing but the activity of men in pursuit of their ends.
    Karl Marx (1818–1883)