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961.
Yuzuru Ito Shigeru Nakashima Hiroyuki Kanoh Yoshinori Nozawa 《Journal of neurochemistry》1997,68(1):419-425
Abstract: The mechanism for carbachol (CCh)-induced phospholipase D (PLD) activation was investigated in [3H]palmitic acid-labeled pheochromocytoma PC12 cells with respect to the involvement of protein tyrosine phosphorylation and Ca2+. PLD activity was assessed by measuring the formation of [3H]phosphatidylbutanol in the presence of 0.3% butanol. Pretreatment of cells with the tyrosine kinase inhibitors herbimycin A, genistein, and tyrphostin inhibited PLD activation by CCh. Western blot analysis revealed several apparent tyrosine-phosphorylated protein bands (111, 91, 84, 74, 65–70, 44, and 42 kDa) in PC12 cells treated with CCh. Phosphorylation of the 111-, 91-, 84-, and 65–70-kDa proteins peaked within 1 min, and their time-dependent changes seemingly correlated with that of PLD activation. Others (74, 44MAPK, and 42MAPK kDa) were phosphorylated rather slowly, and maximal tyrosine phosphorylation was observed at 2 min. Herbimycin A inhibited PLD activity and tyrosine phosphorylation of four proteins (111, 91, 84, and 65–70 kDa) in a preincubation time- and concentration-dependent fashion. In Ca2+-free buffer, CCh-induced [3H]phosphatidylbutanol formation and protein tyrosine phosphorylation were abolished. A Ca2+ ionophore, A23187, caused PLD activation and tyrosine phosphorylation of four proteins of 111, 91, 84, and 65–70 kDa only in the presence of extracellular Ca2+. Extracellular Ca2+ dependency for CCh-induced PLD activation was well correlated with that for tyrosine phosphorylation of the four proteins listed above, especially the 111-kDa protein. These results suggest that Ca2+-dependent protein tyrosine phosphorylation is closely implicated in CCh-induced PLD activation in PC12 cells. 相似文献
962.
Takeshi Minami Masayo Ichii Jiro Okazaki Hideko Kawaki Yuko Okazaki 《Biological trace element research》1996,55(1-2):1-7
We investigated whether free radical scavengers and antioxidants inhibit the accumulation of platinum (Pt) in the cerebral
cortex. Pt was detected in the cerebral cortex of mice afters administration of cisplatin and exposure to short-term hypoxia.
When mice were treated with either allopurinol (20 mg/kg) or catalase (100 mg/kg) before cisplatin administration and low
oxygen exposure, Pt was not detected in the cerebral cortex. However, Pt was detected in the cerebral cortex of mice pretreated
with either a low dosage of allopurinol or heat-denatured catalase. Furthermore, Pt was detected in the cerebral cortex of
mice preadministered vitamin C, vitamin E, or deferoxamine. Lipid peroxide levels in the cerebral cortex increased 10 min
after the treatment of hypoxia, and peaked 30 min after the treatment. These results suggested that short-term hypoxia produces
free radicals, which allows Pt to pass through the blood-brain barrier and accumulate in the cerebral cortex, and that the
production of free radicals is reduced by the administration of either allopurinol or catalase, which prevents Pt from passing
through the barrier. 相似文献
963.
964.
The role of NH+4 ion and AMP deaminase reaction in the activation of phosphofructokinase with respect to its response to the adenylate energy charge was investigated using permeabilized yeast cells. (a) Phosphofructokinase and AMP deaminase were activated by the decrease in the adenylate energy charge. The addition of NH+4 further stimulated the phosphofructokinase activity in the presence of intracellular level of K+, and the optimal energy charge value giving the maximal response of the enzyme was shifted from 0.3 to the value above 0.5. (b) The increase in NH+4 ion produced through the activation of AMP deaminase by spermine which shows no direct action on the phosphofructokinase activity can activate phosphofructokinase with shift of the optimal energy charge value of the enzyme to 0.5 in the presence of K+, whereas the optimal energy charge value for AMP deaminase reaction was not affected by the addition of spermine. Phosphofructokinase can be activated most effectively by the physiological decrease in the energy charge under the condition of increased NH+4 in the presence of K+. The possibility that the interaction of phosphofructokinase with AMP deaminase under hypoxic condition might be a contributing factor to the Pasteur effect is discussed. 相似文献
965.
T Ishizuka K Yasuda N Takeda K Kajita K Miura S Nakashima S Nagao Y Nozawa 《Endocrinologia japonica》1991,38(1):81-87
We have examined thrombin-induced metabolism of phosphoinositides in the platelets from fifteen NIDDM (non-insulin-dependent diabetes mellitus) patients and fifteen healthy subjects (control). The diabetic patients were divided into two groups. One group (group I) had diabetic retinopathy (microangiopathy) and the other group (group II) had atherosclerosis of great vessels (macroangiopathy). In platelets incubated with [32P] orthophosphate for 80 min, the incorporation of 32P radioactivity into phosphatidylinositol (PI), phosphatidylinositol 4-monophosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) was significantly lower in the group II than in the control. The addition of thrombin induced a marked decrease in PIP2 radioactivity at 10 sec in platelets from group I compared with that from the control. These results suggest that the breakdown of polyphosphoinositides is increased in platelets from diabetic subjects with retinopathy, and also that the formation of polyphosphoinositides is decreased in the platelets from diabetic subjects with macroangiopathy. 相似文献
966.
Phospholipase B-like activity in rabbit brain membranes. 总被引:1,自引:0,他引:1
H Kanoh Y Kanaho Y Nozawa 《Comparative biochemistry and physiology. B, Comparative biochemistry》1991,100(2):367-369
1. Phospholipase B-like activity was found in rabbit brain membranes. 2. The activity was greatly enhanced by 0.025% (w/v) Triton X-100 and was inhibited by both Ca2+ and Mg2+. 3. With increasing pH of the reaction mixture, the activity was augmented. 4. The characteristics of the enzyme activity possibly suggest that phospholipase B in rabbit brain may be distinct from those previously reported. 相似文献
967.
968.
Microsomes from Tetrahymena pyriformis catalyzed the conversion of 1-acyl-2-[1-14C]oleoyl-sn-glycero-3-phosphorylcholine to 1-acyl-2-[1-14C]linoleoyl-sn-glycero-3-phosphorylcholine in the presence of oxygen and NADH or NADPH as cofactors. This desaturation enzyme activity was inhibited by cyanide and increased by 0.05-0.1% Triton X-100. Under optimal conditions desaturation appeared to follow Michaelis-Menten kinetics with a Km value of 6.9 . 10(-4) M. During incubation, no significant cleavage of phospholipid substrate was observed and no desaturation of free fatty acid occurred. The activity of 1-acyl-2-oleoyl-sn-glycero-3-phosphorylcholine desaturase was increased approx. 4-fold when Tetrahymena cells were shifted to a lower growth temperature. These data suggest the existence of a direct phospholipid desaturation system from oleoylphosphatidylcholine to linoleoylphosphatidylcholine. In addition, this desaturation may participate in the control of membrane lipid adaptation to a lower growth temperature in Tetrahymena. 相似文献
969.
As the serum transferrin polymorphism was observed in several macaque species, we considered it as one of the best markers
for the study of population genetics of Japanese macaques,Macaca fuscata. In this work the genetic variants of transferrin (Tf) of 1,451 blood samples from 37 troops of this species were tested.
The troops showing the variation of Tf were Fukushima, Yugawara T, Ihama, Ryozenyama, Mikata I and II, Takahama, Takahama
(Otomi), Arashiyama A, Minoh A and B, Kohchi, Mihara, Shimane, and Tomogashima. The wild-type allele of this species was Tf
F, and the variant alleles detected in these troops were E, G−, G, and H′. The alleles E, G and H′ were probably identical with those reported in several macaque species byIshimoto (1972), but the identification of allele G− could not be done. 相似文献
970.
High-level expression of complementary DNA encoding rat calmodulin in Escherichia coli 总被引:2,自引:0,他引:2
S Matsuki T Ozawa S Nagao H Hirata H Kanoh Y Nozawa 《Biotechnology and applied biochemistry》1990,12(3):284-291
We report the production and characterization of a rat calmodulin made in Escherichia coli. To express the rat calmodulin cDNA in E. coli, we have employed an expression vector containing the E. coli trp promoter and trpA terminator. The cDNA was modified so as to delete the 5' nontranslated sequence and to incorporate a consensus sequence for the E. coli ribosome-binding site. Several codons for the N-terminal amino acids were selected to fit the E. coli consensus nucleotide sequence around the translational initiation codon. After induction of expression in E. coli, rat calmodulin accounted for over 30% of total cellular proteins. About 100 mg of recombinant rat calmodulin, purified to over 90% homogeneity by extraction from bacterial lysate followed by phenyl-Sepharose column chromatography, was obtained from 1 liter of E. coli culture. This recombinant calmodulin activated rat brain cyclic AMP phosphodiesterase to the same extent as the native calmodulin purified from rat brain. These results indicate that the overproduction system of the recombinant calmodulin in E. coli facilitates the study of the structure-function relationship by site-specific mutagenesis. 相似文献