Histidine family

Amino Acid Biosynthesis Aromatic amino acid family Aspartate family Glutamate family Pyruvate family Serine family Histidine family Other... 

Another class of PS II inhibitors are phenol-derivatives, liXe the herbicides ioxynil and dinoseb where the QSAR is governed by steric parameters (2), as well as hydroxypyridines (7,8) and Xetoni-triles (9). The two inhibitory families may also be designated as a serine and a histidine families, named after the amino acid in the D-1 polypeptide to which the inhibitor is predominantly oriented (though not necessarly bound) (10). 

The second group of inhibitors, the phenol-type (2) or histidine family ( ) have been shown also to displace each other as well as compounds of the diuron/atrazine family from the membrane (14,29). But these phenol-type inhibitors lacX the essential substructure of the diuron family, as well as the positive n-charge (3.4). Their QSARs point to a large dependence on steric parameters (2). The difference in inhibitory pattern between the two families is reviewed in references (1,10) and an example is given in Table III. 

Step 3 of Figure 29.3 Alcohol Oxidation The /3-hydroxyacyl CoA from step 2 is oxidized to a /3-ketoacyl CoA in a reaction catalyzed by one of a family of L-3-hydroxyacyl-CoA dehydrogenases, which differ in substrate specificity according to the chain length of the acyl group. As in the oxidation of sn-glycerol 3-phosphate to dihydroxyacetone phosphate mentioned at the end of Section 29.2, this alcohol oxidation requires NAD+ as a coenzyme and yields reduced NADH/H+ as by-product. Deprotonation of the hydroxyl group is carried out by a histidine residue at the active site. 

Pyrazol-1 -ylalanine, an isomer of histidine, was isolated from Citrullus vulgaris (watermelon) seed and its structure was confirmed by comparison with synthetic material 107). It was the major free amino acid in the dormant dry seed but was present in only trace amounts in vegetative tissue. While present in seed extracts of other members of the Cucurbitaceae, it has not been identified as occurring in members of other plant families. 

Drosophila DDC belongs to a family of pyridoxal-dependent decarboxylases that extends from prokaryotes to eukaryotic plants and animals. The members of this family show significant sequence similarity over much of their length, even though the individual proteins have quite different substrate specificities, including the amino acids tyrosine, tryptophan, phenylalanine, histidine, and glutamate, and the amino acid derivatives... 

The outstanding inclusion ability and the carboxylic functions of host I raised the idea of co-erystallizing it with imidazole (Im) which, due to its versatile nature 114), is one of the frequently used components in enzyme active sites, generally presented by histidine. Formally, a system made of imidazole and an acid component may mimic two essential components of the so-called catalytic triad of the serine protease family of enzymes the acid function of Aspl02 and the imidazole nucleus of His57 115) (trypsin sequence numbering). The third (albeit essential) component of the triad corresponding to the alcohol function of Seri 95 was not considered in this attempt. This family of enzymes is of prime importance in metabolitic processes. 

Keratinocyte growth factor is a 140 amino acid, 16.3 kDa member of the FGF family. It differs from native keratinocyte growth factor in that the first 23 N-terminal amino acids have been deleted, which improves its stability. After cell growth the product is recovered and purified by a multistep chromatographic protocol. It is presented in lyophilized format in single-use vials and containing mannitol, sucrose, polysorbate 20 and histidine as excipients. It is administered by daily i.v. injection, usually for several days. 

Various spectroscopic methods have been used to probe the nature of the copper centers in the members of the blue copper oxidase family of proteins (e.g. see ref. 13). Prior to the X-ray determination of the structure of ascorbate oxidase in 1989, similarities in the EPR and UV-vis absorption spectra for the blue multi-copper oxidases including laccase and ceruloplasmin had been observed [14] and a number of general conclusions made for the copper centers in ceruloplasmin as shown in Table 1 [13,15]. It was known that six copper atoms were nondialyzable and not available to chelation directly by dithiocarbamate and these coppers were assumed to be tightly bound and/or buried in the protein. Two of the coppers have absorbance maxima around 610 nm and these were interpreted as blue type I coppers with cysteine and histidine ligands, and responsible for the pronounced color of the protein. However, they are not equivalent and one of them, thought to be involved in enzymatic activity, is reduced and reoxidized at a faster rate than the second (e.g. see ref. 16). There was general concurrence that there are two type HI... 

The first class of DUBs discovered, the ubiquitin C-terminal Aydrolases (UCHs), is a relatively small class vith only four members in humans and one in budding yeast. UCHs are cysteine proteases related to the papain family of cysteine proteases. Most UCHs consist entirely of a catalytic core that has a molecular mass of about 25 kDa, although Bapl and UCH37 have C-terminal extensions [21, 22], All UCHs have a highly conserved catalytic triad consisting of the active-site cysteine, histidine, and aspartate residues that are absolutely required for function [23]. 

Comparison within the family of carotenoid oxygenases show that the four histidines are strictly conserved as well as their close environment. Presumably, all members of this family, including the protein catalyzing central cleavage of P-carotene, share a common chain fold, possess similar active centers and follow a similar reaction mechanism, vide infra. 

In addition to the cathelicidins and defensins, humans also utilize a variety of other host defense peptides. Examples of these include the anionic dermcidins, found in human sweat and possessing potent antimicrobial activity in a broad range of pH and salt concentrations, and the histatins, a histidine-rich host defense peptide family found in humans and higher primate species. The histatins are normally found in saliva and utilize an alternative mechanism to bacterial membrane lysis for their antimicrobial activity. ... 

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