Nucleic acids of yeast

Derivation Extracted from nucleic acids of yeast also made synthetically. 

Derivation (Commercial product) Isolation from nucleic acid of yeast or pancreas also made synthetically. 

The high content of nucleic acid in yeast is a potential problem associated with the consumption of large amounts of yeast nucleopro-tein in foods. Phosphorylation is one of the methods used for reducing nucleic acid of yeast proteins (Table 2) [67]. Huang and Kinsella [68] reported the effective removal of nucleic acid from yeast proteins by POCl3-phosphorylation. The phosphorylated protein showed improvement in emulsifying activity and emulsion stability, and produced stable but weak foams at neutral pH. The authors also noted that the in vitro digestibility of yeast protein was not affected by phosphorylation as reported for casein [60] and soy protein [65]. 

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. 

The presence of nucleic acids ia yeast is oae of the maia problems with their use ia human foods. Other animals metabolize uric acid to aHantoia, which is excreted ia the uriae. Purines iagested by humans and some other primates are metabolized to uric acid, which may precipitate out ia tissue to cause gout (37). The daily human diet should contain no more than about 2 g of nucleic acid, which limits yeast iatake to a maximum of 20 g. Thus, the use of higher concentrations of yeast proteia ia human food requires removal of the nucleic acids. Unfortunately, yields of proteia from extracts treated as described are low, and the cost of the proteia may more than double. 

The term nucleoside was originally proposed by Levene and Jacobs in 1909 for the carbohydrate derivatives of purines (and, later, of pyrimidines) isolated from the alkaline hydrolyzates of yeast nucleic acid. The phosphate esters of nucleosides are the nucleotides, which, in polymerized forms, constitute the nucleic acids of all cells.2 The sugar moieties of nucleosides derived from the nucleic acids have been shown, thus far, to be either D-ribose or 2-deoxy-D-eri/fAro-pentose ( 2-deoxy-D-ribose ). The ribo-nucleosides are constituents of ribonucleic acids, which occur mainly in the cell cytoplasm whereas 2-deoxyribo -nucleosides are components of deoxypentonucleic acids, which are localized in the cell nucleus.3 The nucleic acids are not limited (in occurrence) to cellular components. They have also been found to be important constituents of plant and animal viruses. 

Vischer E, Zamenhof S, Chargaff E (1949) Microbial nucleic acids the desoxypentose nucleic acids of avian tubercle bacilli and yeast. J Biol Chem 177 429—438... 

No partly methylated ribose derivatives have been isolated from natural sources up to the present, for although such nucleic acids as yeast nucleic acid contain D-ribose phosphate residues, the methylation technique fails in structural studies in this group because of the hydrolytic action of alkaline reagents. Trimethyl-D-ribofuranose has, how-... 

In summary the deleterious effects of alkali on the proteins and the large-scale impracticality of the heat-shock (endogeneous ribonuclease) process, plus the accompanying proteolysis and denaturation of proteins, clearly indicate the need for better methods to facilitate the large-scale separation of nucleic acids from yeast proteins. 

Another significant problem associated with consumption of microbial cells is their high content of nucleic acid (NA) which ranges from 8 to 25 gms nucleic acid per 100 gms protein and most of the nucleic acid is present as RNA (55). Before single-cell protein can be used as a major source of protein for human consumption, the content of nucleic acid has to be reduced, so that the daily intake of nucleic acid from yeast would not exceed 2 gms (i.e. 20g yeast). Higher quantities cause uricemia and continued ingestion of SCP may result in gout (56,57). 

The [PSP] element is inherited in an orderly, reproducible way but one that is different from most genetic traits (Fig. 1) (Cox, 1965). When a haploid [PSP] strain is mated to a haploid [psi strain, the resulting diploid has a suppression phenotype that is, [PSP] is dominant. On sporulation, however, none of the haploid progeny are [psir] as would be expected for a nuclear determinant Instead, [PSP] is transmitted to all haploid progeny. (The capital letters in [PSP] signify dominance the brackets signify nonchromosomal inheritance.) This unusual pattern of inheritance was partly explained by later experiments that localized the [PS7+] determinant to the cytoplasm (Cox et al, 1980 Fink and Conde, 1976). Surprisingly, however, the [PSP] phenotype could not be linked to any of tbe known cytoplasmic nucleic acids in yeast (Cox et al, 1988 Serio and Lindquist, 1999). 

The nucleic acids were discovered by Miescher in 1868-1869, when he isolated from pus cell nuclei a material which contained phosphorus, was soluble in alkali, but precipitated under acidic conditions. This material was subsequently prepared from other sources and when freed from protein it was called nucleic acid, a term introduced by Altman in 1889. The classical preparations of nucleic acid from yeast yielded a product which we now recognize as ribonucleic acid (RNA). The nucleic acid prepared from thymus glands, thymonucleic acid, was also extensively studied this material [which, in present terms, was deoxyribonucleic acid (DNA)) was different from yeast nucleic acid. From hydrolysates of these preparations the heterocyclic bases were isolated and characterized. At one time, yeast and thymus nucleic acids were thought to be representative of plant and animal nucleic acids, respectively (3). By 1909, it was apparent that yeast nucleic acid contained adenine, guanine, cytosine, uracil, phosphoric acid, and a sugar which Levene showed at that time to be D-ribose. Thymonucleic acid yielded adenine, guanine, cytosine, thymine, phosphoric acid, and a sugar which was not identified correctly until 1929, when it was characterized as 2-deoxy-D-ribose. 

Abrams and co-workers first showed that the precursors of nucleic acid purines were the same as those of uric acid by demonstrating the incorporation of N -glycine into adenine and guanine of the nucleic acids of growing yeast. Heinrich and Wilson, using the rat, also explored the precursors of purines in nucleic acids, and their results confirmed the earlier observations of Buchanan and collaborators for uric acid. It has now been well substantiated that formate, glycine, and CO2 aU con-... 

Biotin was implicated in purine bio thesis by the observations that (a) the fixation of CO2 was markedly lowered in the tissue nucleic acids of biotin-deficient rats S7), and (b) 5-aminoimidazole ribonucleotide accumulated in biotin-deficient yeast 1S8,1S9). In the latter instance, the addition of aspartic acid to the deficient yeast suppressed the accumulation of the arylamine. Since biotin was thought to be involved in aspartic acid biosynthesis (140, 141), it is likely that the synthesis of this amino acid was limiting in biotin deficiency and that the ect of the deficiency on purine biosynthesis was indirect 142),... 

Pentose phosphates occur naturally in the nucleic acids, each of which is made up of four mononucleotides, or glycosides of pentose monophosphate (p. 130). 5-phosphoribose occurs in the nucleic acid of animal chromatin, and in the inosinic and adenylic acid of muscle (p. 291). 3-phosphoribose occurs in the guanylic acid, xanthylic acid and nucleic acid found in yeast (p. 348). 

Nucleic acid contents of SCP products, which range up to 16% in bacteria and 6—11% in yeasts, must be reduced by processing so that intakes are less than 2 g/d to prevent kidney stone formation or gout. Adverse skin and gastrointestinal reactions have also been encountered as a result of human consumption of some SCP products (87). 

Schiestl, R.H. and Gietz, R.D. (1989) High efficiency transformation of intact yeast cells using single stranded nucleic acids as a carrier. Current Genetics, 16 (5-6), 339-346. 

Abecassis, V., Pompon, D. and Truan, G. (2000) High efficiency family shuffling based on multi-step PCR and in vivo DNA recombination in yeast statistical and functional analysis of a combinatorial library between human cytochrome P450 1A1 and 1A2. Nucleic Acids Research, 28, E88. 

The formation of 0-seryl or 0-prolyl esters (Figure 1) of certain N-hydroxy arylamines has been inferred from the observations that highly reactive intermediates can be generated in vitro by incubation with ATP, serine or proline, and the corresponding aminoacyl tRNA synthetases (11,12,119). For example, activation of N-hydroxy-4-aminoquinoline-l-oxide (119,120), N-hydroxy-4-aminoazobenzene (11) and N-hydroxy-Trp-P-2 (121) to nucleic acid-bound products was demonstrated using seryl-tRNA synthetase from yeast or rat ascites hepatoma cells. More recently, hepatic cytosolic prolyl-, but not seryl-, tRNA synthetase was shown to activate N-hydroxy-Trp-P-2 (12) however, no activation was detectable for the N-hydroxy metabolites of AF, 3,2 -dimethyl-4-aminobiphenyl, or N -acetylbenzidine (122). 

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