Guanosine triphosphate , signal

Heme (C34H3204N4Fe) represents an iron-porphyrin complex that has a protoporphyrin nucleus. Many important proteins contain heme as a prosthetic group. Hemoglobin is the quantitatively most important hemoprotein. Others are cytochromes (present in the mitochondria and the endoplasmic reticulum), catalase and peroxidase (that react with hydrogen peroxide), soluble guanylyl cyclase (that converts guanosine triphosphate, GTP, to the signaling molecule 3, 5 -cyclic GMP) and NO synthases. 

G proteins comprise several families of diverse cellular proteins that subserve an equally diverse array of cellular functions. These proteins derive their name from the fact that they bind the guanine nucleotides guanosine triphosphate (GTP) and guanosine diphosphate (GDP) and possess intrinsic GTPase activity. G proteins play a central role in signal transduction as well as in a myriad of cellular processes, including membrane vesicle transport,... 

Nucleotides play central roles in metabolism. They serve as sources of chemical energy (ATP and guanosine triphosphate (GTP)), participate in cellular signalling (cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP)) and are incorporated into important cofactors of enzymatic reactions. Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA (Scheme 3). 

The presence of a nitrogen-containing side chain facilitates interaction with the catalytic site of FPPS, an enzyme in the metabolic pathway that is required for the production of the isoprenoid hpids farnesyl diphosphate and geranylgeranyl diphosphate, essential metabolites for posttranslational protein prenylation [5, 8]. Inhibiting the prenylation of guanosine triphosphate-binding proteins such as Ras, Rho, and Rac disrupts the normal cellular signal transduction that is required for osteoclast function and survival [5]. 

G protein A guanosine triphosphate (GTP)-binding protein that serves as a transducer in a signal transduction pathway. On binding GTP and releasing guanosine diphosphate (GDP), a G protein is able to activate the effector enzyme (e.g., adenylate cyclase). 

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