Inosinic acid hydrolysis

The 3- and 5-phosphates of D-ribose have both been obtained through the hydrolysis of naturally occurring ribosides. In 1908 Levene and Jacobs122 subjected the barium salt of inosinic acid to acid hydrolysis and obtained a pentose phosphate as its barium salt. Shortly thereafter the same authors78 showed that, under the conditions which normally convert a pentose to a pentaric acid, this phosphate was oxidized only to a phosphorylated D-ribonic acid and it was evident, therefore, that... 

Phosphorylation of XLVII with phosphorus oxychloride in pyridine solution, followed by hydrolysis to remove the methyl and isopropylidene residues, gave D-ribose 5-phosphate (XLVIII) which, as its barium salt, was found to be identical with the barium salt of the D-ribose phosphate from inosinic acid. By way of further confirmation of the structure of D-ribose 5-phosphate, Levene, Harris and Stiller129 showed that in methanolic hydrogen chloride solution both the natural and synthetic material mutarotated in a manner characteristic of a sugar which can form only a furanoside. 

Amino acids ate not the only source of ammonium ions produced in the body. Much of the ammonia produced, especially in the brain, arises from the hydrolysis of purines. Adenylate deaminase catalyzes the hydrolysis of AMP, yielding IMP and ammonium ions Cooper and Plum, 1987). IMP is inosine monophosphate (inosinic acid), GMP may also be hydrolyzed in this manner, yielding xanthosine and ammonium ions. Further details on purine metabolism occur at the end of this chapter and under Folate in Chapter 9. 

Historically, this method of stepwise hydrolysis seems to have been first applied to a nucleotide by Levene and Jacobs, in determining the structure of muscle inosinic acid. ... 

On phosphorylation of isopropylidene-inosine, followed by hydrolysis of the acetone residue, muscle inosinic acid (which, as will be seen later, is definitely known to be 5-phospho-inosine) is formed. This confirms the above formulations for isopropylidene-inosine and inosine. 

On neutral hydrolysis of the barium salt it gives barium phosphate and inosine. On hydrolysis with 0.1 AT hydrochloric acid (during 1 hour at 100 ), it gives rise - to hypoxanthine and a phospho-D-ribose. The structure of this phosphoribose was readily shown by oxidation with... 

Inosinic and Adenylic Adds, Similarly, Levene and Harris found that the adenylic acid from ribosenucleic acid can be deaminated to an inosinic acid which undergoes hydrolysis at its own pH to give hypo-xanthine and 3-phosphoribose. On the other hand, Thannhauser had shown that ammoniacal hydrolysis of the adenylic acid gives adenosine and phosphoric acid. 

Inosinic acid (1), the first nucleotide to be discovered, was isolated over a century ago from beef extract by Liebig. Mild, acid hydrolysis of this nucleotide yielded a ribose phosphate (2) which, by oxidation with nitric acid, gave a ribonic acid phosphate (3), but not a ribaric acid phosphate. These studies by Levene and his associates showed that the phosphoric (phospho) group is bound to the 5-hydroxyl group of the ribosyl moiety in 1 hence, inosinic acid is inosine 5 -phosphate. Adenylic acid (4), isolated from muscle, was converted enzymically (by adenylic... 

Oxidation of (8) yielded a ribonic acid phosphate (9), whose properties differed from those of the ribonic acid 5-phosphate obtained by similar hydrolysis and oxidation of inosine 5 -phosphate. Moreover, reduction of (8) allegedly gave a ribitol phosphate (10) which was optically inactive. From these studies, it followed that the phosphoric moiety in (10) is esterified by the 3-hydroxyl group of the ribitol moiety. Similarly, a yeast adenylic acid, obtained from an alkaline hydrolysate of yeast ribonucleic acid, was deaminated to an inosinic acid that was different... 

Mild acid hydrolysis of the deaminated purine nucleotides, xanthylic acid and inosinic acid, gives the purine bases (xanthine and hypo-xanthine, respectively) and a reducing sugar phosphate. The same hydrolytic products are obtained by use of a specific pancreatic enzyme. On the other hand, mild alkaline hydrolysis of a nucleotide, or treatment with the appropriate enzyme, liberates free phosphoric acid and a non-reducing compound of base and sugar, known as a nucleoside. (Hydrolysis of ribosenucleic acid with fairly dilute ammonia under pressure, during 3.5 hours at a bath temperature of 175 to 180 , gives an equimolecular mixture of four nucleosides). 

In the case of DNA, a D-2-deoxyribose molecule is combined to each of the bases to form a nucleoside, and the nucleosides are then combined with each other with a phosphoric acid to form a polymer (DNA). On the other hand, in the case of RNA, D-ribose, instead of D-2-deoxyribose, is combined to each of the bases to form a nucleoside, and as in the case of DNA, these nucleosides are combined with each other to form a polymer (RNA). Among the bases within DNA and RNA, adenine and guanine have been described in the preceding section. In this section, cytosine, thymine, and uracil, which are pyrimidine bases, will be described. Purine derivatives exist as a constituent unit of nucleic acids and as many kinds of monomers, and these are also present in natural products, such as caffeine, inosinic acid, and cytokinin. On the other hand, as natural products, pyrimidine derivatives are rather rare. Nucleosides composed of pyrimidine bases cytosine, thymine, and uracil coupled with D-ribose are known as cytidine, thymidine, and uridine, respectively. Among these alkaloids, cytidine was first isolated from the nucleic acid of yeast [1,2], and thymidine was isolated from thymonucleic acid [3,4]. In the meantime, uridine was obtained by the weak alkali hydrolysis [5] of the nucleic acids originating from yeast. 

Ribose phosphates can be obtained from nucleotides. Mild acid hydrolysis of inosinic acid (12.19a), for example, yields ribose-5 -phosphate and inosine whereas neutral hydrolysis yields inositol and phosphate. 

In 1925, the structure of inosinic acid, which was thought to be the 5 -monophosphate of inosine, was confirmed. Inosinic acid, the first free nucleotide to be recognized, has an interesting history (4). In 1847, the barium salt of this substance was isolated from beef extract by Leibig, who derived the name from the Greek words for muscle fiber. The presence of phosphorus in this substance was not recognized until 1895. In 1909, Levene determined the structure of inosine, a hydrolysis product of inosinic acid, to be the riboside of hypoxanthine with this information, the nucleotide structure of inosinic acid became apparent. 

There are several pathways available for the degradation of the mononucleotides. For example, adenosine 5 -phosphatc (AMP) is either deaminated hydrolytically to inosinic acid (IMP) by 6 -adenylic acid deaminase (217, iS7) or split directly to the corresponding nucleoside, adenosine, by 5 -nucleotidase 238). The nucleoside inosine resulted from either the hydrolysis of inosinic acid by 5 -nucleotidase or by the action of adenosine deaminase on adenosine 238, 239). The above pathways, as well as other likely conversions of purine compounds to hypoxanthine and xanthine 2JiO) are shown in Fig. 13. Finally, the enzyme xanthine oxidase acted on both the free bases, hypoxanthine and xanthine, to produce uric acid which was the final product of purine metabolism in some animals. 

D-Ribose 5-phosphate is a normal metabolite in plants and animals. It was first prepared by acid hydrolysis of inosinic acid or from adenosine 5 -phosphate . It is formed enzymically from ribose and ATP . Synthesis has been carried out by phosphorylating 2,3-isopropylidene-methyl-D-ribofuranoside °. ... 

In a commercially available assay, serum NTP catalyzes the hydrolysis of IMP to yield inosine, which is then converted to hypoxanthine by purine-nucleoside phosphorylase (EC 2.4.2.1). Hypoxanthine is oxidized to urate with xanthine oxidase (EC 1.2.3.2). Two moles of hydrogen peroxide are produced for each mole of hypoxanthine liberated and converted to uric acid. The formation rate of hydrogen peroxide is monitored by a spectrophotometer at 510nm by the oxidation of a chromogenic system. The effect of ALPs on IMP is inhibited by p-glycerophosphate. This material is substrate for ALP but not for NTP, and by forming substrate complexes with the former enzyme, it reduces the proportion of the total ALP activity that is directed to the hydrolysis of the NTP substrate, IMP. ... 

Figure 3.14 Structures of common nucleosides whose acid-catalysed hydrolysis has been studied. Adenosine, guanosine and cytidine are three of the four common nucleosides in RNA and their 2 -deoxy derivatives in DNA, whereas uridine is found only in RNA and 2 -deox5hh5midine in DNA. Psicofuranine is an antibiotic and is not a common constituent of nucleic acids. Inosine is a commonly used substrate in investigations of enzymic ribosyl transfer.

Japan, pat. 732C86) (to Ajinomoto), C.A. 51, 3870b (1957). Structure Levene, Bess, op. ctt.. pp 187-192 Bredereck, Ber. 66, 198 (1933) Levene, Tipson, J. Biol. Chem. Ill, 3t3 (1935). Also prepd from muscle by enzymatic deamination of muscle adenylic acid Ostem, Biochem. Z. 254, 63 (1932) by hydrolysis of inosine triphosphate Kleinzeller, Biochem. J. 36, 729 (1942). Studies on the enzymatic synthesis Greenberg, J. Biol. Chem. 198, 611 (1951) Korn et al, ibid 217, 875 (1955). Microbial fermentation method using mutant strains of Micrococcus glutamicus Kinoshita el al. U.S. pat. 3,232,844 (1966 to Kyowa). 

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