3-methyl histidine excretion

Saundersoa C.L Leslie, S. (1983). N -methyl histidine excretion by poultry not all species exaete N -methyl histidine quantitatively. Br. ]. Nutr., 50, 691-700. 

Saundersoa C.L. Whitehead, C.C. (1987). N Methyl histidine excretion and [U- C] amino acid oxidation in fully fed chickens from two lines for high and low body fat contents. Comp. Biochem. Physiol, 86B, 419-22. 

Experimental animals that have been exposed to ititrous oxide to deplete vitamin B12 show an increase in the proportion of liver folate present as methyl-tetrahydrofolate (85% rather than the normal 45%), largely at the expense of unsubstituted tetrahydrofolate and increased urinary loss of methyl-tetrahydrofolate (Horne et al., 1989). Tissue retention of folate is impaired because methyl-tetrahydrofolate is a poor substrate for polyglutamyl-folate synthetase, compared with unsubstituted tetrahydrofolate (Section 10.2.2.1). As a result of this, vitamin B12 deficiency is frequently accompanied by biochemical evidence of functional folate deficiency, including impaired metabolism of histidine (excretion of formiminoglutamate Section 10.3.1.2) and impaired thymidylate synthetase activity (as shown by abnormally low dUMP suppression Section 10.3.3.3), although plasma concentrations of methyl-tetrahydrofolate are normal or elevated. 

A severe amino aciduria is usually present. All amino acids normally found in the urine, as well as 1-methyl-histidine and 3-methylhistidine, are excreted in excess in advanced cases. The amino add level in the plasma, however, remains normal [40-45]. 

Granerus, G. (1968). Effects of oral histamine, histidine, and diet on urinary excretion of histamine, methylhistamine, and l-methyl-4-imidazoleacetic acid in man, Scand. J. Clin. Lab. Invest., 10, suppl., 49. 

This amino acid which is synthesized by muscle and excreted into urine without recycling has been methylated with [Djj-methyl iodide exclusively at N site and applied as tracer in vivo and as an isotopic dilution standard in vitro, by protecting the N and N positions in a cyclic urea derivative 34. The latter was obtained by treating the (5)-histidine methyl ester 35 with carbonyl diimidazole and hydrolysing the product 36 in boiling dilute hydrochloric acid to give isomerically and isotopically pure title compound 37 retaining at least 95% of its optical rotation (equation 5). 37 has been applied in clinical research. 

Our knowledge of alkaloids in animals is scant. The so-called protoalkaloids (biogenic amines and their derivatives) are widespread in lower animals (194, 195), and the parallelism between plant and animal metabolism is extensive. Betaines, methylated purines (e.g., paraxan-thine (VI) ), derivatives of histidine (spinacine (VII) of the shark), and kynurenic acid (VIII) are not rare in animals. The animal alkaloids, with the exception of samandarine (Vol. V, p. 321), are characterized as weak bases this is perhaps of importance for their excretion. 

The neutral amino acids alanine, serine, threonine, asparagine, glutamine, valine, leucine, isoleucine, phenylalanine, tyrosine, tryptophan, histidine and citrulline share a common transporter at the luminal border of the epithelial cells in the renal tubuli and the epithelial cells in the small intestine [16]. In Hartnup disorder an impairment of this transporter leads to hyperexcretion of these neutral amino acids and to intestinal malabsorption. Excretion of tryptophan metabolites kynurenine and N-methyl-nico-tinamide is reduced. Plasma concentrations of the affected amino acids may be low normal or reduced. The inheritance is autosomal recessive. The hph2-deficient mouse has been postulated as a model for Hartnup disorder [17]. Affected persons may be asymptomatic, while some demonstrate pellagra-like photodermatitis or cerebellar ataxia due to a nicotinamide deficiency and respond well to the administration of nicotinamide [16]. 

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