scholarly journals Adipose-tissue pyruvate kinase. Properties and interconversion of two active forms

1968 ◽  
Vol 110 (1) ◽  
pp. 67-77 ◽  
Author(s):  
C I Pogson
Keyword(s):  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Pyruvate Kinase ◽  
Kinase Activity ◽  
Deae Cellulose ◽  
Epididymal Adipose Tissue ◽  
Partial Purification ◽  
Pyruvate Kinase Activity ◽  
Bivalent Cation

1. Extraction of rat epididymal adipose tissue with buffer containing EDTA yields a pyruvate kinase, provisionally called PyK-A, the properties of which resemble in several respects those of the allosteric pyruvate kinase of liver. These properties include co-operative interactions with phosphoenolpyruvate, Mg2+, K+, NH4+ and ATP, and sensitivity to activation by fructose 1,6-diphosphate. 2. Extraction in the absence of EDTA yields predominantly a form, PyK-B, that shows both normal Michaelis–Menten kinetics with phosphoenolpyruvate, Mg2+ and ATP, and co-operative interactions with K+ and NH4+; this form is insensitive towards fructose 1,6-diphosphate. 3. Both forms yield simple kinetics with ADP, though Km values differ in the two systems. In all cases where co-operativity has been demonstrated, Hill-plot n values are between 1·4 and 2·0. 4. The conversion of PyK-A into PyK-B is mediated specifically by fructose 1,6-diphosphate; the reverse reaction is occasioned by EDTA, ATP or citrate. It is thought that a bivalent cation may be involved in this interconversion. 5. Attempts at partial purification have revealed that the enzyme resembles the pyruvate kinase of skeletal muscle, rather than that of liver, in its solubility in ammonium sulphate and elution from DEAE-cellulose. 6. The relevance of these properties in the regulation of pyruvate kinase activity in vivo in adipose tissue is discussed.

scholarly journals Acute regulation of pyruvate kinase activity in rat epididymal adipose tissue by insulin

1979 ◽  
Vol 180 (3) ◽  
pp. 523-531 ◽  
Author(s):  
R M Denton ◽  
N J Edgell ◽  
B J Bridges ◽  
G P Poole
Keyword(s):  
Pyruvate Kinase ◽  
Kinase Activity ◽  
Covalent Modification ◽  
Epididymal Adipose Tissue ◽  
Pyruvate Kinase Activity ◽  
Marked Diminution ◽  
Fructose 1,6 Bisphosphate ◽  
Fat Pads

1. Evidence is presented that exposure of epididymal fat-pads from fed rats to insulin leads to a marked diminution in the Km for phosphoenolpyruvate of pyruvate kinase. Effects of insulin may be readily demonstrated in experiments both in vivo and in vitro and are not secondary to the activation by the hormone of glucose transport. No effect of insulin is apparent in tissues from 48 h-starved animals. 2. The mechanism of the effect of insulin on pyruvate kinase was not established. The observed changes in Km do not appear to be the result of alterations in the amounts of bound effectors such as fructose 1,6-bisphosphate and alanine. Rather, as the effect persists in incubated extracts, it appears that a change in the degree of phosphorylation or some other covalent modification of the enzyme may be involved.

Pyruvate kinase: modulation by L-phenylalanine and L-alanine

1969 ◽  
Vol 47 (9) ◽  
pp. 895-898 ◽  
Author(s):  
R. Vijayvargiya ◽  
W. S. Schwark ◽  
R. L. Singhal
Keyword(s):  
Skeletal Muscle ◽  
Pyruvate Kinase ◽  
Kinase Activity ◽  
Competitive Inhibitor ◽  
Seminal Vesicles ◽  
Appreciable Effect ◽  
Pyruvate Kinase Activity ◽  
Rat Prostate

L-Phenylalanine was found to be a competitive inhibitor of pyruvate kinase in the rat prostate, seminal vesicles, uterus, and skeletal muscle. In contrast, L-alanine exerted no appreciable effect on pyruvate kinase activity but was capable of protecting against, as well as reversing, the inhibition produced by L-phenylalanine. The results suggest that the interactions between L-phenylalanine and L-alanine are important to the regulation of pyruvate kinase activity in tissues containing the M-type isozyme.

Red blood cell age, pyruvate kinase activity, and insulin receptors. Evidence that monocytes and RBCs may behave differently

Diabetes ◽  
1983 ◽  
Vol 32 (11) ◽  
pp. 1017-1022 ◽  
Author(s):  
A. Camagna ◽  
R. De Pirro ◽  
L. Tardella ◽  
L. Rossetti ◽  
R. Lauro ◽  
...  
Keyword(s):  
Blood Cell ◽  
Pyruvate Kinase ◽  
Red Blood Cell ◽  
Kinase Activity ◽  
Insulin Receptors ◽  
Pyruvate Kinase Activity ◽  
Cell Age

Red Blood Cell Age, Pyruvate Kinase Activity, and Insulin Receptors: Evidence that Monocytes and RBCs May Behave Differently

Diabetes ◽  
1983 ◽  
Vol 32 (11) ◽  
pp. 1017-1022 ◽  
Author(s):  
A. Camagna ◽  
R. D. Pirro ◽  
L. Tardella ◽  
L. Rossetti ◽  
R. Lauro ◽  
...  
Keyword(s):  
Blood Cell ◽  
Pyruvate Kinase ◽  
Red Blood Cell ◽  
Kinase Activity ◽  
Insulin Receptors ◽  
Pyruvate Kinase Activity ◽  
Cell Age

scholarly journals Decreased Akt kinase activity and insulin resistance in C57BL/KsJ-Leprdb/db mice

2000 ◽  
Vol 167 (1) ◽  
pp. 107-115 ◽  
Author(s):  
J Shao ◽  
H Yamashita ◽  
L Qiao ◽  
JE Friedman
Keyword(s):  
Insulin Resistance ◽  
Adipose Tissue ◽  
Glucose Transporter ◽  
Kinase Activity ◽  
Glycogen Synthase ◽  
Glut4 Translocation ◽  
Akt Kinase ◽  
Insulin Signal Transduction ◽  
Kinase Pathway

Recent studies suggest that the serine/threonine kinase protein kinase B (PKB or Akt) is involved in the pathway for insulin-stimulated glucose transporter 4 (GLUT4) translocation and glucose uptake. In this study we examined the components of the Akt signaling pathway in skeletal muscle and adipose tissue in vivo from C57BL/KsJ-Lepr(db/db) mice (db/db), a model of obesity, insulin resistance, and type II diabetes. There were no changes in the protein levels of GLUT4, p85alpha, or Akt in tissues from db/db mice compared with non-diabetic littermate controls (+/+). In response to acute insulin administration, GLUT4 recruitment to the plasma membrane increased twofold in muscle and adipose tissue from +/+ mice, but was significantly reduced by 42-43% (P<0.05) in both tissues from db/db mice. Insulin increased Akt-Ser(473) phosphorylation by two- to fivefold in muscle and adipose tissue from all mice. However, in db/db mice, maximal Akt-Ser(473) phosphorylation was decreased by 32% (P<0.05) and 69% (P<0.05) in muscle and adipose tissue respectively. This decreased phosphorylation in db/db mice corresponded with a significant decrease in maximal Akt kinase activity using a glycogen synthase kinase-3 fusion protein as a substrate (P<0.05). The level of insulin-stimulated tyrosine phosphorylation of p85alpha from phosphatidylinositol 3 (PI 3)-kinase, which is upstream of Akt, was also reduced in muscle and adipose tissue from db/db mice (P<0.05); however, there was no change in extracellular signal-regulated kinase-1 or -2 phosphorylation. These data implicate decreased insulin-stimulated Akt kinase activity as an important component underlying impaired GLUT4 translocation and insulin resistance in tissues from db/db mice. However, impaired insulin signal transduction appears to be specific for the PI 3-kinase pathway of insulin signaling, while the MAP kinase pathway remained intact.

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