The citric acid cycle —also known as the Krebs cycle, Szent-Györgyi-Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. The Krebs cycle is used by organisms that respire (as opposed to organisms that ferment) to generate energy, either by anaerobic respiration or aerobic respiration. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, that are used in numerous other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest components of metabolism. Even though it is branded as a 'cycle', it is not necessary for metabolites to follow only one specific route; at least three alternative segments of the citric acid cycle have been recognized.
Isocitrate dehydrogenase (IDH) (EC 1.1.1.42) and (EC 1.1.1.41) is an enzyme that catalyzes the oxidative decarboxylation of isocitrate, producing alpha-ketoglutarate (α-ketoglutarate) and CO2. This is a two-step process, which involves oxidation of isocitrate (a secondary alcohol) to oxalosuccinate (a ketone), followed by the decarboxylation of the carboxyl group beta to the ketone, forming alpha-ketoglutarate. In humans, IDH exists in three isoforms: IDH3 catalyzes the third step of the citric acid cycle while converting NAD+ to NADH in the mitochondria. The isoforms IDH1 and IDH2 catalyze the same reaction outside the context of the citric acid cycle and use NADP+ as a cofactor instead of NAD+. They localize to the cytosol as well as the mitochondrion and peroxisome.
BRENDA is an information system representing one of the most comprehensive enzyme repositories. It is an electronic resource that comprises molecular and biochemical information on enzymes that have been classified by the IUBMB. Every classified enzyme is characterized with respect to its catalyzed biochemical reaction. Kinetic properties of the corresponding reactants are described in detail. BRENDA contains enzyme-specific data manually extracted from primary scientific literature and additional data derived from automatic information retrieval methods such as text mining. It provides a web-based user interface that allows a convenient and sophisticated access to the data.
Phosphopentose epimerase encoded by the RPE gene is a metalloprotein that catalyzes the interconversion between D-ribulose 5-phosphate and D-xylulose 5-phosphate.
Translocase is a general term for a protein that assists in moving another molecule, usually across a cell membrane. These enzymes catalyze the movement of ions or molecules across membranes or their separation within membranes. The reaction is designated as a transfer from “side 1” to “side 2” because the designations “in” and “out”, which had previously been used, can be ambiguous. Translocases are the most common secretion system in Gram positive bacteria.
In enzymology, a homoisocitrate dehydrogenase (EC 1.1.1.87) is an enzyme that catalyzes the chemical reaction
In enzymology, an amino-acid racemase is an enzyme that catalyzes the chemical reaction
In enzymology, a diaminopimelate epimerase is an enzyme that catalyzes the chemical reaction
In enzymology, an isopenicillin N epimerase is an enzyme that catalyzes the chemical reaction
In enzymology, a protein-serine epimerase is an enzyme that catalyzes the chemical reaction
In enzymology, an UDP-glucuronate 4-epimerase is an enzyme that catalyzes the chemical reaction
The enzyme dihydroneopterin aldolase catalyzes the chemical reaction
The enzyme methylisocitrate lyase catalyzes the chemical reaction
The enzyme 2-methylcitrate dehydratase (EC 4.2.1.79) catalyzes the chemical reaction
The enzyme 2-methylisocitrate dehydratase (EC 4.2.1.99) catalyzes the chemical reaction
The enzyme homoaconitate hydratase (EC 4.2.1.36) catalyzes the chemical reaction
In enzymology, a 2-methylcitrate synthase (EC 2.3.3.5) is an enzyme that catalyzes the chemical reaction
Decylcitrate synthase (EC 2.3.3.2) is an enzyme that catalyzes the chemical reaction in enzymology.
In enzymology, a decylhomocitrate synthase (EC 2.3.3.4) is an enzyme that catalyzes the chemical reaction
In enzymology, an isocitrate O-dihydroxycinnamoyltransferase is an enzyme that catalyzes the chemical reaction
