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.
Glycolysis is the metabolic pathway that converts glucose into pyruvate, and in most organisms, occurs in the liquid part of cells, the cytosol. The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH). Glycolysis is a sequence of ten reactions catalyzed by enzymes.
Gluconeogenesis (GNG) is a metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon substrates. It is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. In vertebrates, gluconeogenesis occurs mainly in the liver and, to a lesser extent, in the cortex of the kidneys. It is one of two primary mechanisms – the other being degradation of glycogen (glycogenolysis) – used by humans and many other animals to maintain blood sugar levels, avoiding low levels (hypoglycemia). In ruminants, because dietary carbohydrates tend to be metabolized by rumen organisms, gluconeogenesis occurs regardless of fasting, low-carbohydrate diets, exercise, etc. In many other animals, the process occurs during periods of fasting, starvation, low-carbohydrate diets, or intense exercise.
In chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed acetate esters or simply acetates. Deacetylation is the opposite reaction, the removal of an acetyl group from a chemical compound.
Histone deacetylases (EC 3.5.1.98, HDAC) are a class of enzymes that remove acetyl groups (O=C-CH3) from an ε-N-acetyl lysine amino acid on both histone and non-histone proteins. HDACs allow histones to wrap the DNA more tightly. This is important because DNA is wrapped around histones, and DNA expression is regulated by acetylation and de-acetylation. HDAC's action is opposite to that of histone acetyltransferase. HDAC proteins are now also called lysine deacetylases (KDAC), to describe their function rather than their target, which also includes non-histone proteins.
The pentose phosphate pathway is a metabolic pathway parallel to glycolysis. It generates NADPH and pentoses as well as ribose 5-phosphate, a precursor for the synthesis of nucleotides. While the pentose phosphate pathway does involve oxidation of glucose, its primary role is anabolic rather than catabolic. The pathway is especially important in red blood cells (erythrocytes).
Pyruvate carboxylase (PC) encoded by the gene PC is an enzyme of the ligase class that catalyzes the physiologically irreversible carboxylation of pyruvate to form oxaloacetate (OAA).
In biochemistry, lipogenesis is the conversion of fatty acids and glycerol into fats, or a metabolic process through which acetyl-CoA is converted to triglyceride for storage in fat. Lipogenesis encompasses both fatty acid and triglyceride synthesis, with the latter being the process by which fatty acids are esterified to glycerol before being packaged into very-low-density lipoprotein (VLDL). Fatty acids are produced in the cytoplasm of cells by repeatedly adding two-carbon units to acetyl-CoA. Triacylglycerol synthesis, on the other hand, occurs in the endoplasmic reticulum membrane of cells by bonding three fatty acid molecules to a glycerol molecule. Both processes take place mainly in liver and adipose tissue. Nevertheless, it also occurs to some extent in other tissues such as the gut and kidney. A review on lipogenesis in the brain was published in 2008 by Lopez and Vidal-Puig. After being packaged into VLDL in the liver, the resulting lipoprotein is then secreted directly into the blood for delivery to peripheral tissues.
Histone acetylation and deacetylation are the processes by which the lysine residues within the N-terminal tail protruding from the histone core of the nucleosome are acetylated and deacetylated as part of gene regulation.
Acetyl-CoA synthetase (ACS) or Acetate—CoA ligase is an enzyme involved in metabolism of acetate. It is in the ligase class of enzymes, meaning that it catalyzes the formation of a new chemical bond between two large molecules.
N-acetylglucosamine-6-sulfatase (EC 3.1.6.14, glucosamine (N-acetyl)-6-sulfatase, systematic name N-acetyl-D-glucosamine-6-sulfate 6-sulfohydrolase) is an enzyme that in humans is encoded by the GNS gene. It is deficient in Sanfilippo Syndrome type IIId. It catalyses the hydrolysis of the 6-sulfate groups of the N-acetyl-D-glucosamine 6-sulfate units of heparan sulfate and keratan sulfate
The enzyme N-acetylgalactosaminoglycan deacetylase (EC 3.1.1.58) catalyzes the reaction
In enzymology, N-acetylglucosamine-6-phosphate deacetylase (EC 3.5.1.25), also known as GlcNAc-6-phosphate deacetylase or NagA, is an enzyme that catalyzes the deacetylation of N-acetylglucosamine-6-phosphate (GlcNAc-6-P) to glucosamine-6-phosphate (GlcN-6-P):
In enzymology, a N-acetylglucosamine deacetylase (EC 3.5.1.33) is an enzyme that catalyzes the chemical reaction
In enzymology, a N-acetylglucosaminylphosphatidylinositol deacetylase (EC 3.5.1.89) is an enzyme that catalyzes the chemical reaction
In enzymology, an indoleacetylglucose-inositol O-acyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a maltose O-acetyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, an indole-3-acetate beta-glucosyltransferase is an enzyme that catalyzes the chemical reaction
Ribostamycin is an aminoglycoside-aminocyclitol antibiotic isolated from a streptomycete, Streptomyces ribosidificus, originally identified in a soil sample from Tsu City of Mie Prefecture in Japan. It is made up of 3 ring subunits: 2-deoxystreptamine (DOS), neosamine C, and ribose. Ribostamycin, along with other aminoglycosides with the DOS subunit, is an important broad-spectrum antibiotic with important use against human immunodeficiency virus and is considered a critically important antimicrobial by the World Health Organization., Resistance against aminoglycoside antibiotics, such as ribostamycin, is a growing concern. The resistant bacteria contain enzymes that modify the structure through phosphorylation, adenylation, and acetylation and prevent the antibiotic from being able to interact with the bacterial ribosomal RNAs.
Chitin disaccharide deacetylase (EC 3.5.1.105, chitobiose amidohydolase, COD, chitin oligosaccharide deacetylase, chitin oligosaccharide amidohydolase) is an enzyme with systematic name 2-(acetylamino)-4-O-(2-(acetylamino)-2-deoxy-beta-D-glucopyranosyl)-2-deoxy-D-glucopyranose acetylhydrolase. This enzyme catalyses the following chemical reaction
