Aspartokinase is an enzyme that catalyzes the phosphorylation of the amino acid aspartate. This reaction is the first step in the biosynthesis of three essential amino acids: methionine, lysine, and serine, known as the "aspartate family". The gene for aspartkinase is present only in microorganisms and plants; it is not present in animals, who must obtain aspartate-family amino acids in their diet. Ribbon diagram of the enzyme TIM. TIM is catalytically perfect, meaning its conversion rate is limited, or nearly limited to its substrate diffusion rate. ... Generic graph showing the effect of a catalyst in an hypothetical exothermic chemical reaction. ... Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule. ... An amino acid residue is what is left of an amino acid once a molecule of water has been lost (an H+ from the nitrogenous side and an OH- from the carboxylic side) in the formation of a peptide bond. ... Aspartic acid, also known as aspartate, the name of its anion, is one of the 20 natural proteinogenic amino acids which are the building blocks of proteins. ... Biosynthesis is a phenomenon where chemical compounds are produced from simpler reagents. ... ‹ The template below has been proposed for deletion. ... Methionine (Met, M. C5H11NO2S) is an essential nonpolar amino acid, and a lipotropic. ... Lysine is one of the 20 amino acids normally found in proteins. ... Serine is one of the 20 natural amino acids. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... E. coli magnified 10,000 times. ... Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants Adiantum pedatum (a fern... Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... Diet may mean: In nutrition: Diet (nutrition), the sum of the food consumed by an organism or group. ...

In E. coli, aspartokinase is present as three independently regulated isozymes, each of which is specific to one of the three downstream biochemical pathways. This allows the independent regulation of the rates of methionine, lysine, and serine production. The forms that produce threonine and lysine are subject to feedback inhibition and all three can be repressed at the level of gene expression by high concentrations of their end products. Binomial name Escherichia coli T. Escherich, 1885 Escherichia coli (usually abbreviated to E. coli) is one of the main species of bacteria that live in the lower intestines of warm-blooded animals (including birds and mammals) and are necessary for the proper digestion of food. ... Isozymes, (or isoenzymes) are isoforms (closely related variants) of enzymes. ... It has been suggested that this article or section be merged with enzyme induction. ... Gene expression, also called protein expression or often simply expression is the process by which a genes DNA sequence is converted into the structures and functions of a cell. ...

External links

• ENZYME entry

References

• Voet D, Voet JG. (2004). Biochemistry Vol 1 3rd ed. Wiley: Hoboken, NJ.