Arginine ammonia formation

Microscopically, it may be difficult to separate heterofermentative cocco bacilloid Leuc oenos) from short bacilloid bacteria Lactobacillus sp). In these cases, Garvie, (1960, 1967) suggests that separation should be made using ammonia formation from arginine. Upon complete conversion of L-arginine, 2NH3 would be expected ... 

Many heterofermentative lactic acid bacteria have the ability to produce energy through the utilization of arginine in formation of ornithine, NH3, CO2, and ATP (Fig. 2.6). The ability of lactic acid bacteria to produce ammonia from arginine can be determined using the method outlined in Section 15.4.1. 

Amino Acids. Traces of amino acids were found in the Devonian Newton Hamilton and Marcellus Formations in a previous study (7). In the present work (Table V) small quantities of amino acids were isolated from the Marcellus shale. In both the earlier work and the present study an amino acid that chromatographed as arginine was found. Other amino acids in the Marcellus black shale are histidine( ), methionine, alanine, tyrosine, valine, leucine or isoleucine, and two unknowns, possibly including aminobutyric acid of nonprotein origin in the Newton Hamilton Formation histidine( ). Ammonia was also present in both the Marcellus and the Newton Hamilton. 

In eukaryotic cells, the two enzymes are in different cellular compartments. Form I uses ammonia and is mitochondrial its function is to provide activated ammonia for arginine biosynthesis (and urea formation during Nitrogen elimination). Form II uses glutamine and is cytoplasmic it functions in pyrimidine biosynthesis. 

The urea so formed is distributed throughout the body water and excreted. The renal clearance of urea is less than the glomerular filtration rate because of passive tubular back-diffusion. Diffusion of urea in the intestine leads to formation of ammonia, which enters the portal blood and is converted to urea in liver. Reentry of ornithine into mitochondria initiates the next revolution of the urea cycle. Ornithine can be converted to glutamate-y-semialdehyde (which is in equilibrium with its cyclic form A -pyrroline-5-carboxylate) by ornithine aminotransferase and de-carboxylated to putrescine by ornithine decarboxylase. Ornithine is also produced in the arginine-glycine trans-amidinase reaction. 

Urea is synthesized in the liver in the urea cycle. The first step is formation of carbamoyl phosphate from ammonia, C02, and ATP. This is followed by a number of other steps, including formation of citrulline, argininosuccinate, and arginine, which is split to urea plus ornithine. The second nitrogen of urea is donated by aspartate in the formation of argininosuccinate. 

Krebs and Henseleit [60] performed key experiments in 1932 by studying the deamination of amino acids, all in in vitro systems. While substituting one amino acid after another for ammonia for the production of urea, they discovered that arginine stimulated urea formation. 

Figure 2.6. Formation of ornithine, ammonia, and carbon dioxide from arginine by some heterofermentative lactic acid bacteria.

From these facts, Ejcbs has explained urea formation in the animal body in terms of an ornithine cycle made up of three stages (i.) Formation of citruUine by condensation of one molecule of ammonia and one of carbon dioxide with the 8-amino group of ornithine, (ii.) formation of arginine by condensation of a second molecule of ammonia with the citrulline, (iii.) decomposition of arginine by arginase, with formation of urea and ornithine, which rejoins the cycle. 

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