Methylated Amino Acid Residues of Proteins of Brain and Other Organs

Abstract

—Methods for the determination of methyl‐lysine, methyllarginine and methylhistidine residues of tissue proteins are described. They consist of preliminary purification of basic amino acids, enzymic removal of lysine, arginine and histidine followed by amino acid analysis. Recovery rates and specificities of the method were satisfactory. The contents of methylamino acids in proteins of mammalian organs were determined. The distribution of proteins containing the methylamino acids in human brain showed that the concentrations of methyl‐lysine and NG,N′G‐dimethylarginine were highest in the gray matter of the cerebellar cortex and relatively high in regions rich in gray matter, while those of NG‐mono‐ and NG,N′G‐dimethylarginine were highest in the white matter. The following findings suggest that most of the NG‐mono‐ and NG,N′G‐dimethylarginine was associated with the myelin basic protein. The distribution of the methylarginine residues of acid‐soluble proteins in bovine brains coincided with the cerebroside pattern. The concentrations of the amino acids in acid‐soluble proteins of rat brain increased concomitantly with the increase of cerebroside. The methylamino acid content in proteins increased during the purification of the myelin basic protein from the white matter of human and bovine brains. Proteins containing NG,NG‐dimethyiarginine and di‐ and trimethyl‐lysine are concentrated in cell nuclei. The first amino acid was found mainly in nucleoplasmic proteins and the other two were found in histones. The concentration of 3‐methylhistidine residue, highest in muscular proteins, is low in cerebral proteins and is probably derived from proteins of walls of blood vessels in the brain.

Asymmetric Dimethylarginine Causes Hypertension and Cardiac Dysfunction in Humans and Is Actively Metabolized by Dimethylarginine Dimethylaminohydrolase

“…The bulk of urinary dimethylamine (260 mol/d, as shown in this study and previous studies 13,28 ) is thought to arise from an endogenous source, 29 suggesting that the rate of ADMA metabolism is in the order of 130 to 260 mol/d compared with a renal excretion rate of approximately 60 mol/d. 2 Consistent with these estimates, the average protein turnover is approximately 300 g/d and the average ADMA content is approximately 1 to 2 mol/g protein, 30 giving a total body production of 300 mol ADMA in 24 hours. Thus, a complete failure of DDAH activity (combined with a loss of renal excretion) would lead to a daily increase in plasma ADMA concentrations by approximately 5 mol/L.…”

Homocysteine Impairs the Nitric Oxide Synthase Pathway

“…This view is supported by the observation that the proportions of methylated and nonmethylated arginine residues on methyl proteins are fairly constant for a given species. 32 Furthermore, dimethylarginine concentrations in urine remain unchanged during a protein-free diet (which would reduce methionine availability). 24 Finally, proteolysis is necessary to release free methylarginine residues.…”

Methylation of elongation factor 1 alpha from the fungus Mucor.

“…Sample processing, two-dimensional gel electrophoresis, gel processing, and fluorography were carried out as described (32 (33), and the resulting fractions were analyzed by two-dimensional TLC on cellulose plates (34) and by dansylation followed by HPLC (35).…”