摘要:

The purification of phosphodiesterase I from hog liver has permitted the demonstration that its properties and catalytic activity are the same as the enzyme previously purified from kidney. The liver, kidney, and snake venom phosphodiesterase I preparations have been compared on the basis of their ability to hydrolyzep-nitrophenyl esters of the 5′-phosphates of thymidine, uridine, and deoxyadenosine at pH 9 in the absence of EDTA versus the activity of potato nucleotide pyrophosphatase, which is active at pH 7 in the presence of EDTA. Kidney microsomes are similarly inactive at the lower pH. Further, the tissue and venom enzymes possess activity against pTpT, TpT, and ribooligonucleotides which are not attacked by the plant nucleotide pyrophosphatase.A comparison of the loss of activity during heating, rates of hydrolysis, kinetics, and competitive inhibition of the animal tissue phosphodiesterase I on several substrates indicates that one catalytic site is responsible for the cleavage of nucleoside 5′-phosphate fromp-nitrophenyl esters, TppT, and NAD+. The tissue enzyme, like the venom enzyme, is active on the 3′-hydroxyl terminus of transfer RNA.

ISSN:0008-4018    

DOI:10.1139/o68-001

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Small amounts ofp-nitrobenzyl alcohol were isolated from chloramphenicol fermentations withStreptomycessp. 3022a. Cultures supplemented withp-aminobenzoic acid also yieldedp-nitrobenzoic acid. Radioactivity fromp-aminobenzoic-ring-14C acid was incorporated more efficiently intop-nitrobenzoic acid than into the alcohol; relatively little appeared in chloramphenicol. A large proportion of the radioactivity was found in the mycelium, from which bound forms of labeledp-nitrobenzoic acid andp-nitrobenzyl alcohol were obtained. The results suggest thatp-aminobenzoic acid is oxidized top-nitrobenzoic acid as a covalent complex, and that part of thep-nitrobenzoic acid produced is converted further top-nitrobenzyl alcohol.

ISSN:0008-4018    

DOI:10.1139/o68-002

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Corticosterone-4-14C was injected intravenously into pregnant mice and fetal tissues were removed after 30 min. Extracts were chromatographed on paper from which zones were eluted and counted. Most counts occurred in the zones representing corticosterone (cpd. B) and 11-dehydrocorticosterone (cpd. A). At a fetal size up to 5 mm crown–rump length (about 11 days), cpd. A constituted 45% of the total counts; this rose as high as 96% (average 80%) in fetuses up to 15 mm. This appeared to be due to increased dehydrogenase activity in fetal tissue; the placenta was also highly active throughout pregnancy. In contrast, late in gestation cpd. A dropped to 24% and this was attributed to the appearance of reductase activity in fetal liver which reduces the metabolite. In young mice for the first 3 weeks of postnatal life the ratio A/B was about 1. Cortisol-4-14C was converted to cortisone but at a slower rate. It was concluded that the 11β-hydroxysteroid dehydrogenase system plays an important role in protecting the fetus from high maternal levels of corticosteroid, but could in some circumstances result in the continued catabolism of biologically active hormone in neonatal life.

ISSN:0008-4018    

DOI:10.1139/o68-003

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

When betaine-1-14C was incubated with cell-free extracts fromAchromobacter cholinophagum, dimethylglycine was found to be labelled and no radioactivity was present in formaldehyde. When betaine-methyl-14C was used as the substrate, both dimethylglycine and formaldehyde contained radioactivity. The results indicate that the formaldehyde is derived from the methyl carbons of betaine. Betaine demethylation activity was decreased by the fractionation of cell-free extracts with ammonium sulfate, and nicotinamide–adenine dinucleotide has been found to restore the activity significantly.

ISSN:0008-4018    

DOI:10.1139/o68-004

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A comparison was made of exo-α-glucanases with α-glucosidases, and of exo-β1 → 3-glucanases with β-glucosidases to establish criteria for their characterization. Dimers, trimers, and tetramers of glucose are substrates for both exo-glucanases and glucosidases. Exo-glucanases act more rapidly on the longer oligomers, glucosidases on the shorter. Exo-glucanases act with inversion of configuration, glucosidases with retention. Other differences are found in transfer activity, in degree of specificity, and in susceptibility to various inhibitors.

ISSN:0008-4018    

DOI:10.1139/o68-005

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Protein nitrogen content, RNA concentration, and in vivo incorporation ofL-[U-14C]leucine into protein and of [2-14C]uridine into RNA of homogenate and various fractions of muscle of normal and dystrophic mice were measured at various stages of the disease. Protein nitrogen content was always lower in dystrophic than in normal muscle, and this became more pronounced with the progress of the disease. Most of the decrease was due to loss of proteins from the myofibrils. RNA content increased in the homogenate, nuclei–myofibrils, supernatant, and microsomes of dystrophic muscle. In the mitochondria of dystrophic muscle, no change was noted compared to controls. The ratio of RNA content to protein in the homogenate, nuclei–myofibrils, supernatant, and microsomes was also greater in dystrophic muscle. It was not changed in dystrophic muscle mitochondria. Incorporation ofL-[U-14C]leucine into proteins of dystrophic muscle homogenate and various fractions also increased to variable degrees over that in the controls. It was further observed that mitochondrial and microsomal protein incorporateL-[U-14C]leucine in dystrophic muscle at an increased rate but the disappearance of14C was even greater, compared to controls.In vivo incorporation of [2-14C]uridine into RNA of dystrophic muscle increased at 30 days', remained the same at 60 days', and declined at 90 days' duration of the disease. Similar results were also obtained in the nuclei–myofibrillar fraction of dystrophic muscle. In all other fractions an increase was noted in incorporation in dystrophic muscle. The incorporation of [2-14C]uridine into RNA in supernatant and microsomes was higher in dystrophic muscle but the disappearance of14C was greater, compared to controls. It is quite evident in the microsomal fraction at 90 days, where no change in the incorporation is noted in normal and dystrophic animals.

ISSN:0008-4018    

DOI:10.1139/o68-006

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Certain compounds, recently introduced as buffers for biological work in the pH range 6–8, were evaluated by measurement of their effects on mitochondrial respiration. Respiratory control, respiration rate, ADP/O ratio, and the effect of added cytochromecwere measured on bean cotyledon mitochondria, after isolation and incubation of the mitochondria in one of five buffers: phosphate, Tris, Tricine (N-tris(hydroxymethyl)methylglycine), TES (N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid), and HEPES (N-2-hydroxyethylpiperazine-N1-2-ethanesulfonic acid). In all parameters measured, except response to added cytochromec, purified TES was found to be superior to all other buffers. HEPES was the best in prevention of leakage of cytochromecfrom the mitochondria but in other respects was similar to Tricine. Phosphate buffer proved superior to Tricine only with respect to cytochromecretention by the mitochondria. Tris was the poorest buffer in which to measure any of these parameters. Aging the mitochondria in the various buffers amplified the inadequacies of the buffers and served to show the superiority of purified TES.

ISSN:0008-4018    

DOI:10.1139/o68-007

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The presence of thyroglobulin in the main peak of a Sephadex G-200 fractionation of a saline extract of human thyroid was detected by Ouchterlony double immuno-diffusion plates against rabbit antihuman thyroglobulin serum.Refiltration of thyroglobulin pooled from the first part of the main peak did not yield a pure native thyroglobulin. A pure 19S component could only be obtained by pooling the effluent corresponding to the descending slopes of the thyroglobulin peaks obtained on the one hand by filtration of the saline extracts, or on the other by refiltration of the effluent corresponding to the ascending slopes of the first filtrations.

ISSN:0008-4018    

DOI:10.1139/o68-008

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The effect of monovalent cations on the ATPase activity of rat liver mitochondria was studied.It was found that alkali-metal ions can activate ATPase when mitochondria become permeable to them by treatment with surface-active agents such as Triton-X-100, alcohols, valinomycin, gramicidin, 2,4-dinitrophenol.The alteration of mitochondrial permeability produced by progressive acidification of the incubation medium indicates that the ability of alkali-metal ions to penetrate mitochondria increases in the order: Li+, Na+, K+, Rb+, and Cs+, which is the order of the decreasing hydrated ionic radii.The results obtained in the presence of valinomycin or gramicidin were comparable with those reported by other workers for the exchange cation–H+. A Na+-activated ATPase could be observed in the presence of high concentrations of valinomycin.The action of surface-active agents on ATPase activity was dependent upon the presence of monovalent cations.It is concluded that control of the metabolism of mitochondria can be exerted through changes in their permeability to cations present in the extramitochondrial cytoplasm.

ISSN:0008-4018    

DOI:10.1139/o68-009

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Using a single litter of seven puppies, it was found that in the period (13–30 weeks of age) when calcification was occurring in most of the ribs there was a change in the extractability of the chondroitin sulfate in this tissue. There was a decrease in the amount of chondroitin sulfate which could be extracted by homogenizing with water and an increase in the amount which was extracted subsequently by homogenization with alkali. This change was not due to binding of chondroitin sulfate to solid mineral matter because it was found also in a single uncalcified rib from an older puppy in which all but the first two anterior ribs were heavily calcified. It was also found when EDTA was used to extract the solid mineral matter. Measurement of specific activities after injection of radioactive sulfate showed that there was little change in the relative rates of synthesis of the water-soluble and water-insoluble chondroitin sulfate fractions as the age of the puppies increased. This leaves a change in the relationship of protein to chondroitin sulfate in complexes of the two as the most likely explanation for the observed change in extractability.

ISSN:0008-4018    

DOI:10.1139/o68-010

出版商:NRC Research Press    

年代:1968

数据来源: NRC