Nucleoprotein, catabolism

Figure 6 is a metabolic map of nucleoprotein catabolism, and Table 6 shows some of the components that can be recovered from scrapings of normal skin, from callus, and from psoriatic scales. In conjunction with the preceding it shows that about 5% of the RNA and less than 1% of the DNA is left in the normal horny layer while up to one-third of the RNA and DNA is still present in the cells of the parakeratotic horny layer of psoriasis. Xanthine and hypoxanthine can be found in psoriatic scales and presumably result from catabolism of nucleic acid purines. Uric acid, although present in the scales, probably comes from the blood, since xanthine oxidase has not been found in human epidermis (B15, B17). Pyrimidine breakdown products have not been found. This might... 

In spite of the catabolism of tissue induced by starvation, the serum protein concentration is little affected initially ultimately, a reduction occurs. However, from the beginning, the catabolism of nucleoproteins causes an increased serum urate. Rise in serum urate is exacerbated by the reduced GFR and the competition for excretion from lactate and ketoacids. 

In addition to their role as components of nucleoproteins, purines and pyrimidines are vital to the proper functioning of the cell. The bases are constituents of various coenzymes, such as coenzyme A (CoA), adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP), diphosphopyridine nucleotide (DPN), triphosphopyridine nucleotide (TPN), and flavin adenine dinucleotide (FAD). A pyrimidine derivative, cytidine diphosphate choline, is involved in phospholipid synthe another pyrimidine compound, uridine diphosphate glucose, is an important substance in carbohydrate metabolism. Cytidine diphosphate ribitol functions in the biosynthesis of a new group of bacterial cell-wall components, the teichoic acids. While mammals excrete nitrogen derived from protein catabolism in the form of urea, birds eliminate their nitrogen by synthesizing it into the purine compound, uric acid. 

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