The PAPs are the classic example of the use of a bimetallic center that contains
ID: 932473 • Letter: T
Question
The PAPs are the classic example of the use of a bimetallic center that contains a trivalent-divalent pair of metal ions to hydrolyze phosphate esters, a notoriously difficult process. Every example of an Fe protein that we discussed during the semester was involved in some sort of electron transfer reaction. Why, then, would organisms ranging from bacteria to plants to mammals use Fe in a hydrolysis reaction? What advantages or disadvantages, if any, does Fe have for use in catalyzing a hydrolytic reaction? What is the likely reason for the presence of a tyrosinate ligand to one Fe^3+ of the binuclear center of the mammalian PAPs?Explanation / Answer
Bifunctional 3'-phosphoadenosine 5'-phosphosulfate synthetase 1 is an enzyme that in humans is encoded by the PAPSS gene.
Three-prime-phosphoadenosine 5-prime-phosphosulfate (PAPS) is the sulfate donor cosubstrate for all sulfotransferase (SULT) enzymes (Xu et al., 2000). SULTs catalyze the sulfate conjugation of many endogenous and exogenous compounds, including drugs and other xenobiotics. In humans, PAPS is synthesized from adenosine 5-prime triphosphate (ATP) and inorganic sulfate by 2 isoforms, PAPSS1 and PAPSS2 (MIM 603005).[supplied by OMIM].
Iron is an essential bioelement for most forms of life, from bacteria tomammals. Its importance lies in its ability to mediate electron transfer. In the ferrous state, iron acts as an electron donor, while in the ferric state it acts as an acceptor. Thus, iron plays a vital role in the catalysis of enzymatic reactions that involve electron transfer (reduction and oxidation, redox). Proteins can contain iron as part of different cofactors, such as iron-sulfur clusters (Fe-S) and hemegroups, both of which are assembled in mitochondria.
Human cells require iron in order to obtain energy as ATP from a multi-step process known as cellular respiration, more specifically from oxidative phosphorylation at the mitochondrial cristae. Iron is present in the iron-sulfur clusters and heme groups of the electron transport chain proteins that generate a proton gradient that allows ATP synthase to synthesize ATP (chemiosmosis).
Heme groups are part of hemoglobin, a protein found in red blood cells that serves to transport oxygen from the lungs to the tissues. Heme groups are also present in myoglobin to store and diffuse oxygen in muscle cells.
he human body needs iron for oxygen transport. Oxygen (O2) is required for the functioning and survival of nearly all cell types (mature erythrocytes being one exception). Oxygen is transported from the lungs to the rest of the body bound to the heme group of hemoglobin in erythrocytes. In muscles cells, iron binds myoglobin, which regulates its release.
Human iron homeostasis is regulated at two different levels. Systemic iron levels are balanced by the controlled absorption of dietary iron by enterocytes, the cells that line the interior of the intestines, and the uncontrolled loss of iron from epithelial sloughing, sweat, injuries and blood loss. In addition, systemic iron is continuously recycled. Cellular iron levels are controlled differently by different cell types due to the expression of particular iron regulatory and transport proteins.
FMS-like tyrosine kinase 3 ligand (Flt3l) is a small molecule that acts as a growth factor that increases the number of immune cells (lymphocytes (B cells and T cells)) by activating the hematopoietic progenitors.
In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP to specific target molecules (substrates); the process is termed phosphorylation. The opposite, an enzyme that removes phosphate groups from targets, is known as a phosphatase. Kinase enzymes that specifically phosphorylate tyrosine amino acids are termed tyrosine kinases.
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