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In biochemistry, isozymes (also known as isoenzymes or more generally as multiple forms of enzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. Isozymes usually have different kinetic parameters (e.g. different K M values), or are regulated differently.
FMO3 is the main flavin-containing monooxygenase isoenzyme that is expressed in the liver of adult humans. [ 8 ] [ 9 ] [ 10 ] The human FMO3 enzyme catalyzes several types of reactions, including: the N -oxygenation of primary, secondary, and tertiary amines ; [ 9 ] [ 11 ] the S -oxygenation of nucleophilic sulfur -containing compounds; [ 9 ...
Hexokinases I, II, and III are referred to as low-K m isoenzymes because of a high affinity for glucose (below 1 mM). Hexokinases I and II follow Michaelis-Menten kinetics at physiological concentrations of substrates. [citation needed] All three are strongly inhibited by their product, glucose-6-phosphate. Molecular masses are around 100 kDa ...
R and T States of Glycogen Phosphorylase b Tower Helices, on the left and right respectively. Note the relative positioning of the central tower helices, as well as the increased interactions between subunits in the R state. PDB3CEH, PDB3E3O. In mammals, the major isozymes of glycogen phosphorylase are found in muscle, liver, and brain. The ...
The most significant difference between the isoenzymes, which allows for selective inhibition, is the substitution of isoleucine at position 523 in COX-1 with valine in COX-2. The smaller Val 523 residue in COX-2 allows access to a hydrophobic side-pocket in the enzyme (which Ile 523 sterically hinders).
Hence, this isoenzyme is an important regulator of glycolysis and additional functions in other novel roles that have recently emerged. Recent evidence indicates that intervening in the complex regulatory network of PKM2 has severe consequences on tumor cell proliferation, indicating the potential of this enzyme as a target for tumor therapy.
Created Date: 8/30/2012 4:52:52 PM
The S-adenosylmethionine synthetase enzyme is found in almost every organism bar parasites which obtain AdoMet from their host. Isoenzymes are found in bacteria, budding yeast and even in mammalian mitochondria. Most MATs are homo-oligomers and the majority are tetramers.