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Y Kuroda

Publications and source records attributed to Y Kuroda.

At least 1,027 records · Page 57Linked to original sources
PubMed1979

Regulatory and functional compartment of three multifunctional protein kinase systems.

Cyclic AMP-dependent protein kinase has been well established to be composed of catalytic and regulatory subunits, and cyclic AMP acts to dissociate these subunits to exhibit full enzymatic activity. In contrast, cyclic GMP-dependent protein kinase does not possess such a subunit structure and is activated by cyclic GMP simply in an allosteric manner. In addition to cyclic AMP-dependent and cyclic GMP-dependent protein kinases, another species of multifunctional protein kinase has been found in many mammalian tissues. This protein kinase is entirely independent of cyclic nucleotides and activated by lower concentrations of Ca2+ in the presence of a membrane-associated factor. This factor has been identified as phospholipids; in fact, phosphatidylinositol and phosphatidylserine are active in this role, whereas lecithin and sphingomyelin are unable to activate the enzyme. Thus, the three species of protein kinases mentioned above are activated in different manners. Nevertheless, these enzymes show very similar substrate specificities and phosphorylate the same specific seryl residues of histone fractions. In addition, all enzymes have abilities to activate and inactivate muscle phosphorylase kinase and glycogen synthetase, respectively, although the relative rates of reactions towards various substrates are markedly different. The Ca2+-dependent protein kinase seems to be associated with membranous components, whereas cyclic GMP-dependent protein kinase appears to be related to certain subcellular organella such as nucleus. Suggestive evidence is available implying that the cyclic AMP-, cyclic GMP- and Ca2+-activated three sets of protein kinase systems may play each specific physiological roles presumably owing to their own subcellular compartments.

Calcium↗
PubMed1979

A comment on the functional specificities of cyclic AMP-dependent and cyclic GMP-dependent protein kinases.

Cyclic AMP-dependent and cyclic GMP-dependent protein kinases (protein kinases A and G, respectively) utilize the same phosphate acceptor proteins when assayed in in vitro systems. Nevertheless, protein kinase A phosphorylates preferentially free histone, whereas protein kinase G greatly favors the histone which is associated with polydeoxyribonucleotide. On the other hand, when cytoplasmic soluble substrates such as phosphorylase kinase are used, the reactions are always more favorable for protein kinase A rather than for protein kinase G. Available evidence implies that the topographic relationship between enzyme and substrate may be an important determining factor for the functional specificities of these two classes of protein kinases.

Cyclic AMP↗
PubMed1979

Abnormal pyruvate and alpha-ketoglutarate dehydrogenase complexes in a patient with lactic acidemia.

Activities of pyruvate decarboxylase (PDC), alpha-ketoglutarate decarboxylase (KGDC) and both the pyruvate and alpha-ketoglutarate dehydrogenase complexes (PDH complex and KGDH complex) were measured, and kinetic properties of PDC were studied in fibroblasts derived from normal individuals and from a 2-yr-old girl with congenital lactic acidemia and severe retardation of growth and development. The activities of PDC, KGDC, PDH complex, and KGDH complex in the patient were 1.12 +/- 0.12, 2.33 +/- 0.42, 9.00 +/- 0.50, and 16.46 +/- 1.57 and in controls 3.10 +/- 0.16, 5.36 +/- 0.56, 24.13 +/- 1.61 and 44.95 +/- 3.72 nmole/mg protein/hr. The optimum pH (6.0) and Michaelis constants (Km) for pyruvate of PDC (1.0-1.6 X 10(-5) M) were similar in fibroblasts of the patient and controls. PDC activity was more sensitive to denaturation by heat in the fibroblasts of the patient than those from controls, while heat denaturation curves of KGDC were similar in the patient and control. Higher concentrations of thiamine pyrophosphate (TPP) were required to protect PDC from heat denaturation in the patient. TPP was more easily removed from PDC in the patient than in the control by washing the fibroblasts with alkaline buffer. These results suggest that the PDC enzyme of the patient is in an altered molecular form, to which TPP is loosely bound. This particular constellation of abnormalities has not previously been reported in patients with lactic acidemia.

Acidosis↗
PubMed1979

Bile duct carcinoma associated with an anomaly in the bile duct.

This paper reports a case of bile duct carcinoma associated with an extra-hepatic bile duct anomaly. In the present case, the anomaly induced an uncorrect preoperative diagnosis and obliged to change the surgical procedures during operation. A correct preoperative diagnosis was difficult to make in the present case, when the anomaly in the biliary system was not kept in mind.

Bile Duct Neoplasms↗
PubMed1978

"Chemical aminoacylation" of tRNA's.

Incubation of abbreviated tRNA's (tRNA-C-COH's) with (chemically) preaminoacylated P1, P2-di(adenosine 5'-)diphosphates in the presence of purified RNA ligase effected transfer of an aminoacyladenylate moiety to the 3'-terminus of the abbreviated tRNA's in good yield. Aminoacylated (or misacylated) tRNA's may thus be prepared from fractionated or unfractionated tRNA-C-COH's; each of the five aminoacylated dinucleoside diphosphates tested was utilized as a substrate by RNA ligase. That the resulting "chemically aminoacylated" tRNA's were identical with those prepared by enzymatic aminoacylation was judged by comparison of 1) chromatographic properties on benzolated diethylaminoethyl-cellulose, 2) rates of chemical deacylation, and 3) affinities for elongation factor Tu, as well as 4) the ability of misacylated tRNA's so derived to be deacylated chemically and then reactivated enzymatically with their cognate amino acids.

Adenine Nucleotides↗
PubMed1978

Monozygotic twins with presumed metachromatic leukodystrophy. Activity of arylsulfatase A in serum of patients and family.

Arylsulfatase A (ASA) activity in urine and serum was assayed on two 21-month-old monozygotic twins with presumed metachromatic leukodystrophy (MLD), their parents, and kin. The patients showed a marked reduction in ASA activity in both urine and serum. The twins' parents and 11 kin, a total of 13 persons, were examined for ASA activity in serum, but it was not possible to delineate heterozygous carriers of MLD by the present study. The assay of ASA activity in serum promises to be useful for diagnosis of MLD.

Cerebroside-Sulfatase↗
PubMed1978

Dose-rate effects of ethyl methanesulfonate on survival and mutation induction in cultured Chinese hamster cells.

The dose-rate effects of ethyl methanesulfonate (EMS) on the survival and induction of mutations in Chinese hamster Don cells were investigated. The most effective time of exposure to EMS for reducing the surviving fraction of cells was 4 h, shorter and longer exposure times being less effective. The threshold or minimal concentration of EMS giving a surviving fraction of 0.5 was 0.05 mg/ml. The minimal effective time of exposure to EMS for cell death was 1 h. Corrected survival curves showed that longer exposure times at lower dose rates of EMS had less cytotoxic effect than shorter exposure times at higher dose rates. After exposure of Don cells to various doses of EMS for various times, the frequencies of mutations resistant to 6--thioguanine (6TG) were measured. An exposure time of 4 h produced a lower mutation frequency than shorter or longer exposure times that resulted in the same surviving fraction of cells. An exposure time of 20 h produced the highest induced mutation frequency. This system using cultured Chinese hamster cells should be useful as a sensitive procedure for detecting the mutagenic actions of chemicals.

Cell Line↗
PubMed1978

Physiological roles of adenosine derivatives which are released during neurotransmission in mammalian brain.

1. Experiments using synaptosome beds suggested that ATP was released from presynaptic sites and degraded to adenosine in the synaptic cleft and that the resulting adenosine was taken up again into nerve endings where it was re-phosphorylated to ATP. 2. Adenosine derivatives in the synaptic cleft inhibited the postsynaptic potentials in olfactory cortex slices in vitro, presumably by the inhibition of Ca2+ influx into nerve endings which resulted in the reduction of transmitter release. 3. The adenosine derivatives also increased the level of cyclic AMP in the slices under the same conditions as above. 4. Although the nature of the "adenosine receptors" for both functions was remarkably similar, the increase of cyclic AMP did not mediate the inhibitory action, but the presynaptic increase of cyclic AMP induced by adenosine derivatives might mediate the facilitation observed in the olfactory cortex. 5. Possible physiological roles of extracellular adenosine derivatives in mammalian brain were classified, at different sites of action around the synapses, with different time courses and modes of action, directly or via the increase of intracellular cyclic AMP.

Adenine Nucleotides↗
PubMed1977

Stimulatory effect of histones on phosphorylation of nuclear phosphoproteins.

Effect of histones on phosphorylation of nuclear phosphoproteins was studied using two species of phosphoprotein kinases with different kinetic and catalytic properties; namely, protein kinases A1 and A2 (Takeda, M., Matsumura, S., & Nakaya, Y. (1974) J. Biochem. 75, 743-751). The reaction rate for protein kinase A1 was markedly enhanced when histone or polylysine was added to the reaction mixture. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the basic protein served as a stimulator rather than acted as a substrate in this reaction. In contrast, when protein kinase A2 was employed, the stimulatory action of these basic proteins was less marked than for protein kinase A1. It seems likely that the phosphorylation of nuclear phosphoproteins, particularly the reaction catalyzed by protein kinase A1, may be strongly influenced by histones which are integrated in the chromatin structure.

Animals↗