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51.
52.
Pullulanase synthesis in Klebsiella (Aerobacter) aerogenes strains growing in continuous culture 总被引:5,自引:0,他引:5 下载免费PDF全文
1. Pullulanase synthesis was studied in 16 classified (N.C.I.B.) strains and in an industrial strain (R) of Klebsiella aerogenes grown in chemostats containing maltose as inducer and sole carbon source. 2. Maximum synthesis was associated with carbon-limited growth at a low dilution rate (about 0.2h(-1)). The enzyme remained firmly cell-bound and seemed to be located on the cell surface. 3. Three strains had high activity (R, N.C.I.B. 5938, 8017), twelve were intermediate, and two (N.C.I.B. 8153, 9146) had negligible activity but were inducible with pullulan. 4. Pullulan similarly induced low, but adequate, activity in the other strains in conditions (nutrient limitation other than carbon-limitation) in which pullulanase was otherwise very seriously repressed. Nevertheless, in carbon limitation pullulan induced no more enzyme than did maltose, maltotriose or oligosaccharide mixtures, and ;hyperactivity' never developed on protracted culture. 5. Cyclic AMP relieved the transient repression produced by adding glucose to maltose-limited cultures and a further change to glucose-limited conditions led to constitutive pullulanase synthesis. 6. Amylomaltase and alpha-glucosidase activities were also examined but in less detail. 7. The presence of pullulanase in maltose-limited growth is discussed, but no clear function can be assigned to it at present. The molar growth yields for all the strains were very similar, and no correlation was found between the overgrowth of one strain by another and pullulanase activity. Further, any function as a general branching enzyme in polysaccharide synthesis seems unlikely. 相似文献
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Although indirect evidence has implicated Delta(5,7,24)-cholestatrien-3-ol as a possible intermediate in cholesterol biosynthesis, this sterol has not previously been isolated from tissues. Administration of two inhibitors of cholesterol biosynthesis to pigs led to the accumulation of Delta(5,7,24)-cholestatrien-3-ol in the tissues, and this sterol was isolated from the lung. Proof of its chemical identity was based upon UV, IR, NMR, circular dichroism, and mass spectra, as well as comparison with synthetic Delta(5,7,24)-cholestatrien-3-ol. A fragment at m/e 143 is particularly prominent in the mass spectrum of Delta(5,7)-sterols, and this fact may prove useful for the detection of this functional group. It is proposed that Delta(5,7,24)-cholestatrien-3-ol may be an intermediate in sterol biosynthesis in both animals and plants. 相似文献
56.
A method previously reported for detecting virus in a model system composed of cottage cheese contaminated with coxsackievirus type A9 has been adapted to detecting selected strains of enteroviruses in a variety of foods. Bentonite is omitted and serum is added for extracting virus from low-protein foods. Samples of foods, usually 25 g, must contain at least 3 to 4 plaque-forming units for a 50% probability of detecting virus. Sensitivity in detecting echovirus type 6 was lower than that for the other viruses used. After extraction from potato salad, poliovirus type 2 was completely reactivated if it had been neutralized with coproantibody, but it was only partially reactivated if neutralized with hyperimmune rabbit serum. 相似文献
57.
A soluble 2,3-oxidosqualene sterol cyclase 总被引:5,自引:0,他引:5
P D Dean P R Ortiz de Montellano K Bloch E J Corey 《The Journal of biological chemistry》1967,242(12):3014-3015
58.
Metabolism of [1-14C]glyoxylate, [1-14C]-glycollate, [1-14C]glycine and [2-14C]-glycine by homogenates of kidney and liver tissue from hyperoxaluric and control subjects 总被引:1,自引:1,他引:0 下载免费PDF全文
1. The metabolism of [1-(14)C]glyoxylate to carbon dioxide, glycine, oxalate, serine, formate and glycollate was investigated in hyperoxaluric and control subjects' kidney and liver tissue in vitro. 2. Only glycine and carbon dioxide became significantly labelled with (14)C, and this was less in the hyperoxaluric patients' kidney tissue than in the control tissue. 3. Liver did not show this difference. 4. The metabolism of [1-(14)C]glycollate was also studied in the liver tissue; glyoxylate formation was demonstrated and the formation of (14)CO(2) from this substrate was likewise unimpaired in the hyperoxaluric patients' liver tissue in these experiments. 5. Glycine was not metabolized by human kidney, liver or blood cells under the conditions used. 6. These observations show that glyoxylate metabolism by the kidney is impaired in primary hyperoxaluria. 相似文献
59.
The wrestler's ear 总被引:2,自引:0,他引:2
J C Kelleher J G Sullivan G J Baibak R K Dean 《Plastic and reconstructive surgery》1967,40(6):540-546
60.
1. 26-Hydroxycholesterol was obtained by reducing the methyl ester of (±)-3β-hydroxycholest-5-en-26-oic acid, which was synthesized from 25-oxonorcholesterol. 2. Methods for preparing 7α-hydroxycholesterol and 7-dehydrocholesterol were modified to allow the micro-scale preparation of these [14C]sterols from [26-14C]-cholesterol. 3. 26-Hydroxycholesterol was oxidized more readily than 7α-hydroxycholesterol, 7-dehydrocholesterol or cholesterol by mitochondrial preparations from livers of mice, rats, guinea pigs, common toads (Bufo vulgaris) and Caiman crocodylus. 4. (±)-3β-Hydroxy[26-14C]cholest-5-en-26-oic acid was oxidized very rapidly to 14CO2 by mouse and guinea-pig mitochondria without evident discrimination between the two optical isomers. 5. An enzyme system that oxidizes 26-hydroxycholesterol to 3β-hydroxycholest-5-en-26-oic acid was identified in the soluble extract of rat-liver mitochondria. This enzyme could use NADP in place of NAD but was not identical with liver alcohol dehydrogenase (EC 1.1.1.1). 6. [26-14C]Cholesteryl 3β-sulphate was not oxidized by fortified mouse-liver preparations that oxidized [26-14C]cholesterol to 14CO2. 相似文献