Use of multiple isotope effects to determine enzyme mechanisms and intrinsic isotope effects. Malic enzyme and glucose 6-phosphate dehydrogenase

Biochemistry ◽  
1982 ◽  
Vol 21 (20) ◽  
pp. 5106-5114 ◽  
Author(s):  
Jeffrey D. Hermes ◽  
C. A. Roeske ◽  
Marion H. O'Leary ◽  
W. W. Cleland
Keyword(s):  
Malic Enzyme ◽  
Isotope Effects ◽  
Enzyme Mechanisms ◽  
Glucose 6 Phosphate Dehydrogenase

Multiple isotope effects with alternative dinucleotide substrates as a probe of the malic enzyme reaction

Biochemistry ◽  
1991 ◽  
Vol 30 (23) ◽  
pp. 5755-5763 ◽  
Author(s):  
Paul M. Weiss ◽  
Sandhya R. Gavva ◽  
Ben G. Harris ◽  
Jeffrey L. Urbauer ◽  
W. W. Cleland ◽  
...  
Keyword(s):  
Malic Enzyme ◽  
Isotope Effects ◽  
Enzyme Reaction

Determination of the Chemical Mechanism of Malic Enzyme by Isotope Effects†

Biochemistry ◽  
1997 ◽  
Vol 36 (5) ◽  
pp. 1141-1147 ◽  
Author(s):  
William A. Edens ◽  
Jeffrey L. Urbauer ◽  
W. W. Cleland
Keyword(s):  
Malic Enzyme ◽  
Isotope Effects ◽  
Chemical Mechanism

Hormonal regulation of malic enzyme and glucose-6-phosphate dehydrogenase in brown adipose tissue

1993 ◽  
Vol 264 (6) ◽  
pp. E874-E881 ◽  
Author(s):  
S. D. Carvalho ◽  
N. Negrao ◽  
A. C. Bianco
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Malic Enzyme ◽  
Hormonal Regulation ◽  
Inhibitory Effect ◽  
Thyroid Status ◽  
Brown Adipose ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Dose Dependent ◽  
Intact Rats

The activities of malic enzyme (ME) and glucose-6-phosphate dehydrogenase (G-6-PDH), two NADPH-generating lipogenic enzymes, were measured in brown adipose tissue (BAT) of rats undergoing various neurohormonal manipulations. Methimazole-induced hypothyroidism doubled the activity of these two enzymes but, surprisingly, triiodothyronine (T3) given to hypothyroid rats caused a time- and dose-dependent stimulation of up to three- to fourfold. Unilateral BAT denervation modestly reduced the activity of these enzymes (approximately 30%) and failed to prevent the stimulation induced by hypothyroidism, whereas growth hormone (GH) successfully blocked this effect of hypothyroidism. Insulin stimulated both enzymes regardless of the thyroid status but failed to abolish the inhibitory effect of GH. In intact rats, cold exposure caused a time-dependent increase in the activity of both ME and G-6-PDH, which reached 5.2- and 3-fold, respectively, after 96 h. This cold-induced stimulation was not observed in hypothyroid rats, but it was restored by physiological doses of thyroxine (800 ng.100 g body wt-1.24 h-1). Replacement with T3 (300 ng.100 g body wt-1.24 h-1), in contrast, did not have this effect. In hypothyroid rats with hemidenervation of BAT, norepinephrine (NE) modestly increased ME and G-6-PDH activities in the denervated side, with little or no effect in the intact side. Receptor-saturating doses of T3 (50 micrograms.100 g body wt-1.day-1 over 48 h) stimulated two- and threefold both enzymes in both sides, reducing or obliterating the effect of denervation. The data suggest a complex neurohormonal regulation of the activity of ME and G-6-PDH in BAT.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanistic deductions from isotope effects in multireactant enzyme mechanisms

Biochemistry ◽  
1981 ◽  
Vol 20 (7) ◽  
pp. 1790-1796 ◽  
Author(s):  
Paul F. Cook ◽  
W. W. Cleland
Keyword(s):  
Isotope Effects ◽  
Enzyme Mechanisms

Determination of the rate-limiting steps for malic enzyme by the use of isotope effects and other kinetic studies

Biochemistry ◽  
1977 ◽  
Vol 16 (4) ◽  
pp. 571-576 ◽  
Author(s):  
Michael I. Schimerlik ◽  
C. E. Grimshaw ◽  
W. W. Cleland
Keyword(s):  
Malic Enzyme ◽  
Isotope Effects ◽  
Kinetic Studies ◽  
Rate Limiting

Metal Ion Activator on Intrinsic Isotope Effects of Hydride Transfer and Decarboxylation in the Reaction Catalyzed by the NAD-Malic Enzyme from Ascaris suum

Biochemistry ◽  
1995 ◽  
Vol 34 (10) ◽  
pp. 3253-3260 ◽  
Author(s):  
William E. Karsten ◽  
Sandya R. Gavva ◽  
Sang-Hoon Park ◽  
Paul F. Cook
Keyword(s):  
Malic Enzyme ◽  
Metal Ion ◽  
Ascaris Suum ◽  
Isotope Effects ◽  
Hydride Transfer
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