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β-lactam antibiotics are antibiotics that contain a beta-lactam ring in their chemical structure. This includes penicillin derivatives (penams), cephalosporins and cephamycins (cephems), monobactams, carbapenems and carbacephems. Most β-lactam antibiotics work by inhibiting cell wall biosynthesis in the bacterial organism and are the most widely used group of antibiotics. Until 2003, when measured by sales, more than half of all commercially available antibiotics in use were β-lactam compounds. The first β-lactam antibiotic discovered, penicillin, was isolated from a strain of Penicillium rubens.
Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the amino and guanidino groups are protonated, resulting in a cation. Only the l-arginine (symbol Arg or R) enantiomer is found naturally. Arg residues are common components of proteins. It is encoded by the codons CGU, CGC, CGA, CGG, AGA, and AGG. The guanidine group in arginine is the precursor for the biosynthesis of nitric oxide. Like all amino acids, it is a white, water-soluble solid.
Ornithine is a non-proteinogenic amino acid that plays a role in the urea cycle. Ornithine is abnormally accumulated in the body in ornithine transcarbamylase deficiency. The radical is ornithyl.
Arginase (EC 3.5.3.1, arginine amidinase, canavanase, L-arginase, arginine transamidinase) is a manganese-containing enzyme. The reaction catalyzed by this enzyme is:
Agmatine, also known as 4-aminobutyl-guanidine, was discovered in 1910 by Albrecht Kossel. It is a chemical substance which is naturally created from the amino acid arginine. Agmatine has been shown to exert modulatory action at multiple molecular targets, notably: neurotransmitter systems, ion channels, nitric oxide (NO) synthesis and polyamine metabolism and this provides bases for further research into potential applications.
Clavulanic acid is a β-lactam drug that functions as a mechanism-based β-lactamase inhibitor. While not effective by itself as an antibiotic, when combined with penicillin-group antibiotics, it can overcome antibiotic resistance in bacteria that secrete β-lactamase, which otherwise inactivates most penicillins.
Spermine is a polyamine involved in cellular metabolism that is found in all eukaryotic cells. The precursor for synthesis of spermine is the amino acid ornithine. It is an essential growth factor in some bacteria as well. It is found as a polycation at physiological pH. Spermine is associated with nucleic acids and is thought to stabilize helical structure, particularly in viruses. It functions as an intracellular free radical scavenger to protect DNA from free radical attack. Spermine is the chemical primarily responsible for the characteristic odor of semen.
A catalytic triad is a set of three coordinated amino acids that can be found in the active site of some enzymes. Catalytic triads are most commonly found in hydrolase and transferase enzymes. An acid-base-nucleophile triad is a common motif for generating a nucleophilic residue for covalent catalysis. The residues form a charge-relay network to polarise and activate the nucleophile, which attacks the substrate, forming a covalent intermediate which is then hydrolysed to release the product and regenerate free enzyme. The nucleophile is most commonly a serine or cysteine amino acid, but occasionally threonine or even selenocysteine. The 3D structure of the enzyme brings together the triad residues in a precise orientation, even though they may be far apart in the sequence.
The enzyme argininosuccinate lyase (EC 4.3.2.1, ASL, argininosuccinase; systematic name 2-(N ω-L-arginino)succinate arginine-lyase (fumarate-forming)) catalyzes the reversible breakdown of argininosuccinate:
Amino acid synthesis is the set of biochemical processes by which the amino acids are produced. The substrates for these processes are various compounds in the organism's diet or growth media. Not all organisms are able to synthesize all amino acids. For example, humans can synthesize 11 of the 20 standard amino acids. These 11 are called the non-essential amino acids).
Carbamoyl phosphate synthetase catalyzes the ATP-dependent synthesis of carbamoyl phosphate from glutamine or ammonia and bicarbonate. This enzyme catalyzes the reaction of ATP and bicarbonate to produce carboxy phosphate and ADP. Carboxy phosphate reacts with ammonia to give carbamic acid. In turn, carbamic acid reacts with a second ATP to give carbamoyl phosphate plus ADP.
The crotonase family comprises mechanistically diverse proteins that share a conserved trimeric quaternary structure, the core of which consists of 4 turns of a (beta/beta/alpha)n superhelix.
In enzymology, an agmatine deiminase (EC 3.5.3.12) is an enzyme that catalyzes the chemical reaction
In enzymology, a creatininase (EC 3.5.2.10) is an enzyme that catalyses the hydrolysis of creatinine to creatine, which can then be metabolised to urea and sarcosine by creatinase.
In enzymology, a guanidinobutyrase (EC 3.5.3.7) is an enzyme that catalyzes the chemical reaction
In enzymology, a N-formylglutamate deformylase (EC 3.5.1.68) is an enzyme that catalyzes the chemical reaction
In enzymology, a proclavaminate amidinohydrolase (EC 3.5.3.22) is an enzyme that catalyzes the chemical reaction
In enzymology, a N2-(2-carboxyethyl)arginine synthase (EC 2.5.1.66) is an enzyme that catalyzes the chemical reaction
Carboxylesterase, type B is a family of evolutionarily related proteins that belongs to the superfamily of proteins with the Alpha/beta hydrolase fold.
The haloacid dehydrogenase superfamily is a superfamily of enzymes that include phosphatases, phosphonatases, P-type ATPases, beta-phosphoglucomutases, phosphomannomutases, and dehalogenases, and are involved in a variety of cellular processes ranging from amino acid biosynthesis to detoxification.
References
- ↑ Ureohydrolases at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- 1 2 Lee J, Suh SW, Kim KH, Kim D, Yoon HJ, Kwon AR, Ahn HJ, Ha JY, Lee HH (2004). "Crystal structure of agmatinase reveals structural conservation and inhibition mechanism of the ureohydrolase superfamily". J. Biol. Chem. 279 (48): 50505–13. doi: 10.1074/jbc.M409246200 . PMID 15355972.
- ↑ Christianson DW, Di Costanzo L, Sabio G, Mora A, Rodriguez PC, Ochoa AC, Centeno F (2005). "Crystal structure of human arginase I at 1.29-A resolution and exploration of inhibition in the immune response". Proc. Natl. Acad. Sci. U.S.A. 102 (37): 13058–13063. doi: 10.1073/pnas.0504027102 . PMC 1201588 . PMID 16141327.
- 1 2 Clifton IJ, Elkins JM, Hernandez H (2002). "Oligomeric structure of proclavaminic acid amidino hydrolase: evolution of a hydrolytic enzyme in clavulanic acid biosynthesis". Biochem. J. 366 (Pt 2): 423–434. doi:10.1042/BJ20020125. PMC 1222790 . PMID 12020346.
- ↑ Baker BS, Tata JR, Xu Q (1993). "Developmental and hormonal regulation of the Xenopus liver-type arginase gene". Eur. J. Biochem. 211 (3): 891–898. doi: 10.1111/j.1432-1033.1993.tb17622.x . PMID 7916684.
- ↑ Ahn HJ, Kim KH, Lee J, et al. (November 2004). "Crystal structure of agmatinase reveals structural conservation and inhibition mechanism of the ureohydrolase superfamily". J. Biol. Chem. 279 (48): 50505–13. doi: 10.1074/jbc.M409246200 . PMID 15355972.
- ↑ "IPR006035 Ureohydrolase" . Retrieved 2009-02-17.
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