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81.
The two steps in the side-chain cleavage of C21 steroids to give C19 steroids (i.e. 17 alpha-hydroxylation and C17,20 lyase activity) were examined using a highly purified cytochrome P-450 from microsomes of neonatal pig testis to determine the photochemical action spectra for the two reactions. Photochemical action spectra, using either 4-ene (progesterone) or 5-ene (pregnenolone) substrates, showed maximal reversal of inhibition by CO with light of 451 nm. Evidently the heme of cytochrome P-450 is involved in both 17 alpha-hydroxylation and in C17,20-lyase activity as in the case of the side-chain cleavage of cholesterol. Mechanisms proposed to account for enzymatic cleavage of the alpha-ketol side-chain of C21 steroids (C17,20 lyase activity) must be consistent with these findings. 相似文献
82.
Cabbage (Brassica oleracea var capitata) leaves were used as a source of cystine lyase. Diethylaminoethyl-cellulose chromatography resolved two peaks of activity, designated I and II. 相似文献
83.
Joanna Strosznajder Laurie Foudin Wilson Tang Grace Y. Sun 《Journal of neurochemistry》1983,40(1):84-90
Arachidonate incorporation into synaptosomal phospholipids was shown to be affected by factors including the procedure for preparation of the membrane fractions and preincubation of synaptosomes prior to assay of incorporation of arachidonate into both phosphatidylcholine (PC) and phosphatidylinositol (PI). However, the inhibition toward incorporation into PIs, but not PCs, was fully reversed when the membranes were washed with bovine serum albumin. A twofold increase in arachidonate incorporation into PIs was also observed when freshly prepared synaptosomes were washed with serum albumin immediately before assay of incorporation activity. The inhibitory action is thought to be due to an increase in polyunsaturated fatty acids and/or their oxidation products which may then elicit a special effect on the acyltransferase responsible for transferring arachidonate into phosphatidylinositols. The differences in fatty acid uptake and response to serum albumin also suggest the presence of different acyltransferase for acyl transfer to PIs and PCs. 相似文献
84.
85.
86.
Summary Exudate can be obtained from incisions made in the bark of the stem of actively growing Ricinus plants. 14C-labelled assimilates from a fed leaf are rapidly detected in the exudate. This movement was both acropetal and basipetal from the fed leaf, at rates of over 100 cm h-1. Estimated rates within intact plants were 80–84 cm h-1.In contrast with xylem sap obtained from the same plant, the exudate obtained had an alkaline pH (8.2), a high dry matter content (10–12.5%), high sugar content (8–10%) which was predominantly sucrose; high potassium content (60–80 mM) and low calcium content (0.5–1.0 mM).It is concluded, on the basis of the present evidence, that the exudate is a true sample of the sieve tube sap undergoing translocation. 相似文献
87.
Regulation of Newly Evolved Enzymes. I. Selection of a Novel Lactase Regulated by Lactose in ESCHERICHIA COLI 总被引:17,自引:2,他引:15 下载免费PDF全文
Thirty-four lactose-utilizing strains of E. coli were selected from a lac Z deletion strain. In 31 of these, the synthesis of the newly evolved lactase is regulated by lactose. The lactase activity in all the strains is indistinguishable from the ebg(+) activity identified by Campbell, Lengyel and Langridge (1973). 相似文献
88.
The exchange of glucose across the liver cell membrane 总被引:2,自引:0,他引:2
G Hetenyi K H Norwich D R Studney J D Hall 《Canadian journal of physiology and pharmacology》1969,47(4):361-367
89.
Synthesis of 2-thio-5-carboxymethyluridine methyl ester: a component of transfer RNA 总被引:1,自引:0,他引:1
L Baczynskyj K Biemann M H Fleysher R H Hall 《Canadian journal of biochemistry》1969,47(12):1202-1203
90.
J. L. Hall 《Planta》1969,89(3):254-265
Summary The distribution of ATP-ase and other nucleotide phosphatases has been studied in young root tips of maize, barley and broad bean using frozen and paraffin sections stained by standard lead sulphide precipitation procedures. High ATP-ase activity was found at the root and cell surface which is in agreement with previous biochemical studies using excised roots and cell wall preparations. Staining was also found in the nuclei and at particulate sites in the cytoplasm. Differences were observed between the present work and the staining pattern obtained for -glycerophosphatase, and between ATP-ase staining in the three roots studied. These results are discussed in relation to the possible physiological activity of the enzymes and to the differences found between earlier histochemical studies of ATP-ase activity.Abbreviations F.L.
frozen longitudinal
- F.T.
frozen transverse 相似文献