Tryptophan cytochrome

Various histidine-, tryptophan-, cysteine-containing proteins, BSA, HSA, y-globulin, liver catalase, IgG, concanavalin A, ovalbumin, lysozyme, histidine/tryptophan, cytochrome c, ribonuclease A, chymotrypsinogen A Enzymes Antigen/antibody Receptor... 

Various minor hematological effects have been noted in animals. Rats exposed to 50-800 ppm of trichloroethylene continuously for 48 or 240 hours showed time- and dose-related depression of delta-aminolevulinate dehydratase activity in liver, bone marrow, and erythrocytes (Fujita et al. 1984 Koizumi et al. 1984). Related effects included increased delta-aminolevulinic acid (ALA) synthetase activity, reduced heme saturation of tryptophan pyrrolase and reduced cytochrome P-450 levels in the liver and increased urinary excretion of... 

HULL, A.K., VU, R., CELENZA, J.L., Arabidopsis cytochrome P450s that catalyze the first step of tryptophan-dependent indole-3-acetic acid biosynthesis, Proc. Natl. Acad. Sci. USA, 2000,97,2379-2384. 

MIKKELSEN, M.D., HANSEN, C.H., WITTSTOCK, U., HALKIER, B.A., Cytochrome P450 CYP79B2 from Arabidopsis catalyzes the conversion of tryptophan to indole-3-acetaldoxime, a precursor of indole glucosinolates and indole-3-acetic acid, J. Biol. Chem., 2000, 275,33712-33717. 

In one series of experiments the cytochrome c oxidase mutations replaced acidic residues by neutral ones, and some of them were thus expected to alter the nature of binding of the protein to cytochrome c. From the pattern of dependence of the heme c to Cua electron-transfer rate constant on these mutations it was deduced that the binding of cytochrome c to cytochrome c oxidase is mediated by electrostatic interactions between four specific acidic residues on cytochrome c oxidase and lysines on cytochrome c. In another series of experiments, tryptophan 143 of cytochrome c oxidase was mutated to Phe or Ala. These mutations had an insignificant effect on the binding of the two proteins, but they dramatically reduced the rate constant for electron transfer from heme c to Cua- It was concluded that electron transfer from... 

Some tryptophans do not exhibit phosphorescence because of quenching by specific sites from within the protein. The absence of phosphorescence could be due to quenching of either the singlet state or the triplet state. For example, in horse heart cytochrome c the tryptophan is adjacent to the heme, and its fluorescence is quenched by Forster transfer to the heme. Since the singlet state is populating the triplet state, the lack of observable phosphorescence is likely to be due to an unpopulated triplet state. Another example where the redox center of the protein interacts with the tryptophan excited states is found in azurin. The copper(II) quenches both the singlet and triplet states.(28)... 

The following is review on the molecular and physical properties of this class of monooxygenases, which are also known as hydroxylases. A typical monooxygenase reaction is the hydroxylation of an alkane to an alcohol which involves a reduced cosubstrate that reduces a second atom within the O2 molecule to form water. Flavin-containing monooxygenases include lysine oxygenase and 4-hydroxybenzoate hydroxylase. Reduced pteri-dines are involved in the phenylalanine hydroxylase and tryptophan hydroxylase reactions. See also Cytochrome P-450... 

The enzymes that are involved in the conversion of tyrosine to the aldoximes, 25 and 26 02.105 pj tryptophan , phenylalanine , valine and isoleucine " to the corresponding aldoximes are the multifunction cytochrome P450. CYP79A1, that hydroxylates tyrosine, was isolated from Sorghum bichlor and subsequently cloned". These oximes are the building blocks of plant glucosinolates, 15, and glycosides, 16. 

Arabidopsis cytochrome P450 (CYP79B2 and CYP79B3) Conversion of tryptophan to indole acetaldoxime 119... 

Munro, A. W., et al. (1992) Investigating the function of cytochrome P450 BM-3 a role for the phylogenetically conserved tryptophane residue. Biochem. Soc. Trans. 21, 66. 

The great difficulty in understanding the evolution of a protein can be illustrated by cytochromes c, which are known to have a methionine and a histidine as heme ligands. The position of the methionine, especially, in the sequence of the proteins is very variable. Again cytochromes c have very different molecular weights. If this is true what is the implication for the overall fold The immediate neighbors of the heme, not bound to iron, include a tryptophan, almost invariable in structure but not in sequence position. How has this been evolved There is but one cytochrome c that has no tryptophan. I do not believe that we could follow evolution with confidence from sequences of single enzymes. Cytochrome c3 sequences show this very clearly, for these proteins, all from sulfur bacteria, show an enormous sequence variation [R. P. Ambler, Syst. Zool. 22, 554 (1974)]. There is no evidence that this is related to their evolution. 

Cytochrome c oxidase contains one heme a and one heme a, besides two copper atoms Cu EPR detectable when oxidized and CUj EPR undetectable With L-tryptophan 2,3-dioxygenase (EC 1.13.11.11), another heme protein, it has been... 

Structure and use of porphyrins Porphyrins are cyclic compounds that readily bind metal ions—usually Fe2+ or Fe3+ The most prevalent metalloporphyrin in humans is heme, which is found in hemoglobin, myoglobin, cytochromes, and the enzymes catalase and tryptophan pyrrolase. 

Figure 16-9 Stereoscopic a-carbon plot of yeast cytochrome c peroxidase (top) and yeast cytochrome c (below) as determined from a cocrystal by Pelletier and Kraut.164 The heme rings of the two proteins appear in bold lines, as does the ring of tryptophan 191 and the backbone of residues 191 — 193 of the cytochrome c peroxidase. Drawing from Miller et al.165...

Because the three-dimensional structures of the peroxidase, its reductant cytochrome c, and the complex of the two (Fig. 16-9) are known, cytochrome c peroxidase is the subject of much experimental study. Other fungal peroxidases, some of which contain manganese rather than iron, act to degrade lignin (Chapter 25).218 A lignin peroxidase from the white wood-rot fungus Phanerochaete chrysosporium has a surface tryptophan with a specifically hydroxylated C(3 carbon atom which may have a functional role in catalysis.2183 0... 

C, 22 h, 0.2% tryptamine 61 High recoveries of tryptophan from cytochrome C... 

AH the above statements are illustrated by Figure 6.2, where a probable mechanism for complex I cytochrome-c-peroxidase formation and conversion is shown. The participation of two water molecules was not shown in the layout (H20 595 and H20 648) [98], One of these molecules (H20 595) is axially bound to iron ion and by hydrogen bonds to His 552 and Trp (tryptophane) 51 fragments. The second molecule (H20 648) is bound by hydrogen bonds to the axial water molecule and Arg 48. It is the authors opinion [98] that fixed positions of these water molecules form something of a model of the enzyme-substrate complex I, in which O2 atom in the substrate RO1—02H substitutes axial water molecule 595, and O1 atom-water molecule 648. 

Figure 6.2 also shows X radical formation. For heme enzymes, this radical is described from positions of location and origin of distal amino-acid residues. For example, in the case of the cytochrome-c-peroxidase complex above discussed, this Trp 51 is easily forming an indole radical. In the case of catalase and vegetable peroxidase this position is occupied by Phe (phenylalanine) which is oxidized much harder than tryptophane. Hence, heme oxidation becomes predominant. 

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