Arginine hydrolysis

Manganese Arginase Arginine hydrolysis, urea cycle... 

STEP 4 OF FIGURE 20.5 ARGININE HYDROLYSIS The final step to complete the urea cycle is hydrolysis of arginine to give ornithine and urea. The reaction is catalyzed by the Mn " -containing enzyme arginase and occurs by addition of H2O to the C=N" " bond, followed by proton transfer and elimination of ornithine from the tetrahedral intermediate. 

M.p. 207°C. The naturally occurring substance is dextrorotatory. Arginine is one of the essential amino-acids and one of the most widely distributed products of protein hydrolysis. It is obtained in particularly high concentration from proteins belonging to the prolamine and histone classes. It plays an important role in the production of urea as an excretory product. 

M.p. 140°C. An amino-acid occasionally formed in the hydrolysis products of proteins and occurring in the urine of some birds as dibenzoylornithine. Ornithine is a precursor of arginine in plants, animals and bacteria. 

FIGURE 27 19 Proposed mechanism of hydrolysis of a peptide catalyzed by carboxypeptidase A The peptide is bound at the active site by an ionic bond between its C terminal ammo acid and the positively charged side chain of arginine 145 Coordination of Zn to oxygen makes the carbon of the carbonyl group more positive and increases the rate of nucleophilic attack by water... 

Trypsin (Section 27 10) A digestive enzyme that catalyzes the hydrolysis of proteins Trypsin selectively catalyzes the cleavage of the peptide bond between the carboxyl group of lysine or arginine and some other amino acid... 

Fig. 12. Tryptic map of it-PA (mol wt = 66,000) showing peptides formed from hydrolysis of reduced, alkylated rt-PA. Separation by reversed-phase octadecyl (C g) column using aqueous acetonitrile with an added acidic agent to the mobile phase. Arrows show the difference between A, normal, and B, mutant rt-PA where the glutamic acid residue, D, has replaced the normal arginine residue, C, at position 275.

All the residues involved in important functions in the catalytic mechanism are strictly conserved in all homologous GTPases with one notable exception. Ras does not have the arginine in the switch 1 region that stabilizes the transition state. The assumption that the lack of this catalytically important residue was one reason for the slow rate of GTP hydrolysis by Ras was confirmed when the group of Alfred Wittinghofer, Max-Planck Institute,... 

Over 30 amino acids have been identified in the hydrolysis product of casein of which glutamic acid, hydroxyglutamic acid, proline, valine, leucine and lysine comprise about 60%. The residues of the aminoacid arginine also appear to be of importance in the cross-linking of casein with formaldehyde. 

Partial hydrolysis of a peptide can be carried out either chemically with aqueous acid or enzymatically. Acidic hydrolysis is unselective and leads to a more or less random mixture of small fragments, but enzymatic hydrolysis is quite specific. The enzyme trypsin, for instance, catalyzes hydrolysis of peptides only at the carboxyl side of the basic amino acids arginine and lysine chymotrypsin cleaves only at the carboxyl side of the aryl-substituted amino acids phenylalanine, tyrosine, and tryptophan. 

GTP-binding protein at an arginine residue which is involved in GTP hydrolysis. ADP-ribosylation thus leads to constitutive activation of Gs. 

Lewis-Acid Catalyzed. Recently, various Lewis acids have been examined as catalyst for the aldol reaction. In the presence of complexes of zinc with aminoesters or aminoalcohols, the dehydration can be avoided and the aldol addition becomes essentially quantitative (Eq. 8.97).245 A microporous coordination polymer obtained by treating anthracene- is (resorcinol) with La(0/Pr)3 possesses catalytic activity for ketone enolization and aldol reactions in pure water at neutral pH.246 The La network is stable against hydrolysis and maintains microporosity and reversible substrate binding that mimicked an enzyme. Zn complexes of proline, lysine, and arginine were found to be efficient catalysts for the aldol addition of p-nitrobenzaldehyde and acetone in an aqueous medium to give quantitative yields and the enantiomeric excesses were up to 56% with 5 mol% of the catalysts at room temperature.247... 

The proportions of the amino acids obtained by hydrolysis in green and roasted coffee beans differs (see Table 12).3 Arginine, cystine, histi-... 

Moser et al. (1968) (one of the co-authors was Clifford Matthews) reported a peptide synthesis using the HCN trimer aminomalonitrile, after pre-treatment in the form of a mild hydrolysis. IR spectra showed the typical nitrile bands (2,200 cm ) and imino-keto bands (1,650 cm ). Acid hydrolysis gave only glycine, while alkaline cleavage of the polymer afforded other amino acids, such as arginine, aspartic acid, threonine etc. The formation of the polymer could have occurred according to the scheme shown in Fig. 4.9. 

Pathy, L., and Smith, E.L. (1975) Reversible modification of arginine residues Application to sequence studies by restriction of tryptic hydrolysis to lysine residues./. Biol. Chem. 250, 557. 

Measurements other than respiration rate can also be used as indicators of soil microbial activity. These include measurements of the rate of multienzyme processes such as arginine ammonification rate (Alef and Kleiner 1995) fluorescein diacetate (FDA) hydrolysis rate (Alef 1995) and measurement of key endocellular enzymes such as dehydrogenase (Tabatabai 1994). 

Fig. 15. H-Ras mGTP shows a transient increase in fluorescence signal when mixed with the catalytic domain of the Ras-GAP neurofibromin (NF1). When wildtype NF1 is applied (gray trace) a decrease in signal follows, indicating the hydrolysis of mant-GTP. A NF1 mutant bearing an alanine at the position of the catalytic arginine residue (black trace) can only bind to Ras mant-GTP (increase) but cannot induce mant-GTP hydrolysis (no decrease). Figure kindly committed by Reza Ahmadian...

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