Of arginine

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. 

Protamines. Strongly basic, low mol. wt. proteins which contain high levels of arginine, but no sulphur-containing amino-acids. They are soluble proteins, associated with nucleic acids and are obtained in large quantity from fish spermatozoa. 

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... 

RL Cutler, AM Davies, S Creighton, A Warshel, GR Moore, M Smith, AG Mauk. Role of arginine-38 in regulation of the cytochrome c oxidation-reduction equilibrium. Biochemistry 28 3188-3197, 1989. 

Certain amino acids and their derivatives, although not found in proteins, nonetheless are biochemically important. A few of the more notable examples are shown in Figure 4.5. y-Aminobutyric acid, or GABA, is produced by the decarboxylation of glutamic acid and is a potent neurotransmitter. Histamine, which is synthesized by decarboxylation of histidine, and serotonin, which is derived from tryptophan, similarly function as neurotransmitters and regulators. /3-Alanine is found in nature in the peptides carnosine and anserine and is a component of pantothenic acid (a vitamin), which is a part of coenzyme A. Epinephrine (also known as adrenaline), derived from tyrosine, is an important hormone. Penicillamine is a constituent of the penicillin antibiotics. Ornithine, betaine, homocysteine, and homoserine are important metabolic intermediates. Citrulline is the immediate precursor of arginine. 

One step in the urea cycle for ridding the body of ammonia is the conversion of argininosuccinate to the amino acid arginine plus fumarate. Propose a mechanism for the reaction, and show the structure of arginine. 

Cleavage of Arginine Releases Urea Re-forms Ornithine... 

Figure 30-3. Top Catabolism of proline. Numerals indicate sites of the metabolic defects in type I and type II hyper-prolinemias. Bottom Catabolism of arginine. Glutamate-y-semialdehyde forms a-ketoglutarate as shown above. , site of the metabolic defect in hyperargininemia.

NO synthase catalyzes a five-electron oxidation of an amidine nitrogen of arginine. L-Hydroxyarginine is an intermediate that remains tighdy bound to the en-... 

Two intact units of acetate were incorporated into neosaxitoxin as evidenced by the appearance of two sets of AB type signals in the C-NMR spectrum. The orientation of the incorporated acetate units was determined by feeding [2- Cjacetate as shown in Scheme 2. This result clearly excludes the original pathway in which C-5 should come from C-1 of arginine. 

The C-NMR spectrum of neosaxitoxin obtained from the feeding experiment showed an enhanced signal for C-4, which was split into a doublet by the spin-spin coupling with the neighboring (J=9.3 Hz) (Scheme 4). The result clearly indicate that the connectivity C-2 - N-2 of arginine was incorporated intact into the toxin molecule, supporting the pathway in Scheme 3. 

SUGANO M, ISHIWAKI N, NAKASHIMA K (1984) Dietary protein-dependent modification of serum cholesterol level in rats significance of Arginine/lysine ratio. rinw Nutr Metab, 28 192-9. 

The best known catabolic pathways of nitrogenous compounds are those of arginine, proline, allantoin and 4-aminobutyrate (GABA) degradation. Each of these is inducible under specific conditions, and all are subject to nitrogen-catabo-lite repression (see [7,9] and section 6.3). 

Reactions involving carbamyl phosphate in the degradation of arginine in Clostridia, and the fermentation of allantoin by Streptococcus allantoicus... 

In contrast to the deleterious effects of arginine described by Buisson, L-arginine was shown to decrease infarct size caused by middle cerebral artery occlusion in spontaneously hypertensive rats. L-Arginine is a precursor for NO synthesis by NOS. The authors attributed the protection to dilation of cerebral blood vessels by NO (Morikawa et 1992). These examples illustrate the difficulty that the NO villain/protector paradox presents to us. 

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