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.
The branched-chain α-ketoacid dehydrogenase complex is a multi-subunit complex of enzymes that is found on the mitochondrial inner membrane. This enzyme complex catalyzes the oxidative decarboxylation of branched, short-chain alpha-ketoacids. BCKDC is a member of the mitochondrial α-ketoacid dehydrogenase complex family comprising pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, key enzymes that function in the Krebs cycle.
Ethanol, an alcohol found in nature and in alcoholic drinks, is metabolized through a complex catabolic metabolic pathway. In humans, several enzymes are involved in processing ethanol first into acetaldehyde and further into acetic acid and acetyl-CoA. Once acetyl-CoA is formed, it becomes a substrate for the citric acid cycle ultimately producing cellular energy and releasing water and carbon dioxide. Due to differences in enzyme presence and availability, human adults and fetuses process ethanol through different pathways. Gene variation in these enzymes can lead to variation in catalytic efficiency between individuals. The liver is the major organ that metabolizes ethanol due to its high concentration of these enzymes.
In enzymology, a 2-hydroxyquinoline 8-monooxygenase (EC 1.14.13.61) is an enzyme that catalyzes the chemical reaction
In enzymology, a 3-hydroxyphenylacetate 6-hydroxylase (EC 1.14.13.63) is an enzyme that catalyzes the chemical reaction
In enzymology, a 4-hydroxybenzoate 1-hydroxylase (EC 1.14.13.64) is an enzyme that catalyzes the chemical reaction
4-hydroxyphenylacetate 3-monooxygenase (EC 1.14.14.9) is an enzyme that catalyzes the chemical reaction
In enzymology, an alkene monooxygenase (EC 1.14.13.69) is an enzyme that catalyzes the chemical reaction
In enzymology, a cholesterol 7alpha-monooxygenase (EC 1.14.13.17) is an enzyme that catalyzes the chemical reaction
In enzymology, a flavonoid 3'-monooxygenase (EC 1.14.14.82, was wrongly classified as EC 1.14.13.21 in the past) is an enzyme that catalyzes the chemical reaction
In enzymology, an imidazoleacetate 4-monooxygenase (EC 1.14.13.5) is an enzyme that catalyzes the chemical reaction
In enzymology, a (R)-limonene 6-monooxygenase (EC 1.14.13.80) is an enzyme that catalyzes the chemical reaction
In enzymology, a salicylate 1-monooxygenase (EC 1.14.13.1) is an enzyme that catalyzes the chemical reaction
In enzymology, a (S)-limonene 6-monooxygenase (EC 1.14.13.48) is an enzyme that catalyzes the chemical reaction
In enzymology, a (S)-limonene 7-monooxygenase (EC 1.14.13.49) is an enzyme that catalyzes the chemical reaction
In enzymology, a steroid 17alpha-monooxygenase (EC 1.14.99.9) is an enzyme that catalyzes the chemical reaction
Methanesulfonate monooxygenase (EC 1.14.13.111, mesylate monooxygenase, mesylate,reduced-FMN:oxygen oxidoreductase, MsmABCD, methanesulfonic acid monooxygenase, MSA monooxygenase, MSAMO) is an enzyme with systematic name methanesulfonate,NADH:oxygen oxidoreductase. This enzyme catalyses the following chemical reaction
Cholest-4-en-3-one 26-monooxygenase (EC 1.14.13.141, CYP125, CYP125A1, cholest-4-en-3-one 27-monooxygenase) is an enzyme with systematic name cholest-4-en-3-one,NADH:oxygen oxidoreductase (26-hydroxylating). This enzyme catalyses the following chemical reaction
3-ketosteroid 9alpha-monooxygenase (EC 1.14.13.142, KshAB, 3-ketosteroid 9alpha-hydroxylase) is an enzyme with systematic name androsta-1,4-diene-3,17-dione,NADH:oxygen oxidoreductase (9alpha-hydroxylating). This enzyme catalyses the following chemical reaction
L-ornithine N5 monooxygenase (EC 1.14.13.195 or EC 1.14.13.196) is an enzyme which catalyzes one of the following chemical reactions:
L-ornithine + NADPH + O2 N(5)-hydroxy-L-ornithine + NADP+ + H2O L-ornithine + NAD(P)H + O2 N(5)-hydroxy-L-ornithine + NAD(P)+ + H2O
