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Biosynthesis of an insulin precursor by islet tissue of cod (Gadus callarias).

ABSTRACT: 1. At 15 degrees , slices of cod islet tissue incorporated [U-(14)C]proline into proteins soluble in acid-ethanol at a linear rate for 6hr. 2. Initially, all the radioactivity was associated with a polypeptide that had a molecular weight of about 10000 and was appreciably more basic than cod insulin. After 1hr. there was also a significant and progressive increase in the radioactivity of insulin and of fractions intermediate in molecular size and basicity between the polypeptide and insulin. 3. O-Ethyl O-p-nitrophenyl phenylpropylphosphonate markedly decreased the radioactivity both of the intermediate fractions and of insulin, but had no significant effect on the biosynthesis of the polypeptide. In contrast, puromycin inhibited the incorporation of radioactivity into all the fractions. 4. The polypeptide had an activity of less than 0.2 international unit/mg. in the epididymal-fat-pad bioassay. Treatment with low concentrations of trypsin caused a progressive increase in the formation of an insulin-like material, judged by bioassay and ion-exchange chromatography of the digest. 5. Gel filtration of the polypeptide after oxidative sulphitolysis indicated that it was a single polypeptide chain. 6. The results suggest that the polypeptide is an insulin precursor whose formation is inhibited by puromycin and that the steps involved in the conversion of precursor into product are sensitive to O-ethyl O-p-nitrophenyl phenylpropylphosphonate.

SUBMITTER: Grant PT

PROVIDER: S-EPMC1187207 | biostudies-other | 1968 Nov

REPOSITORIES: biostudies-other

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Project description:The eastern Baltic cod (Gadus morhua) population has been decreasing in the Baltic Sea for at least 30 years. Condition indices of the Baltic cod have decreased, and previous studies have suggested that this might be due to overfishing, predation, lower dissolved oxygen or changes in salinity. However, numerous studies from the Baltic Sea have demonstrated an ongoing thiamine deficiency in several animal classes, both invertebrates and vertebrates. The thiamine status of the eastern Baltic cod was investigated to determine if thiamine deficiency might be a factor in ongoing population declines. Thiamine concentrations were determined by chemical analyses of thiamine, thiamine monophosphate and thiamine diphosphate (combined SumT) in the liver using high performance liquid chromatography. Biochemical analyses measured the activity of the thiamine diphosphate-dependent enzyme transketolase to determine the proportion of apoenzymes in both liver and brain tissue. These biochemical analyses showed that 77% of the cod were thiamine deficient in the liver, of which 13% had a severe thiamine deficiency (i.e. 25% transketolase enzymes lacked thiamine diphosphate). The brain tissue of 77% of the cod showed thiamine deficiency, of which 64% showed severe thiamine deficiency. The thiamine deficiency biomarkers were investigated to find correlations to different biological parameters, such as length, weight, otolith weight, age (annuli counting) and different organ weights. The results suggested that thiamine deficiency increased with age. The SumT concentration ranged between 2.4-24 nmol/g in the liver, where the specimens with heavier otoliths had lower values of SumT (P = 0.0031). Of the cod sampled, only 2% of the specimens had a Fulton's condition factor indicating a healthy specimen, and 49% had a condition factor below 0.8, indicating poor health status. These results, showing a severe thiamine deficiency in eastern Baltic cod from the only known area where spawning presently occurs for this species, are of grave concern.

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Biosynthesis of an insulin precursor by islet tissue of cod (Gadus callarias).

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