citrate - zkadhem

[ArchivalUser]

The activity of which of the following enzymes is directly affected by citrate?
A. Fructose-2,6-bisphosphatase
B. Isocitrate dehydrogenase
C. Phosphofructokinase I
D. Pyruvate carboxylase
E. 6-phosphogluconate dehydrogenase

[ArchivalUser]

b..

[ArchivalUser]

I THINK CC

[ArchivalUser]

Explanation:
The correct answer is C. Citrate is produced by citrate synthase from acetyl CoA and oxaloacetate.
This reaction takes place in the mitochondria, but citrate can move freely from the mitochondria into
the cytosol. When the citric acid cycle slows down, citrate accumulates. In the cytosol, it acts as a
negative allosteric regulator of phosphofructokinase I, the enzyme that catalyzes the committed step
of glycolysis.
Fructose-2,6-bisphosphatase (choice A) breaks down fructose-2,6-bisphosphate, a potent allosteric
activator of phosphofructokinase I. Fructose-2,6-bisphosphatase is activated by cyclic AMP-dependent
protein kinase.
Isocitrate dehydrogenase (choice B) converts isocitrate to alpha-ketoglutarate in the citric acid
cycle. It is allosterically stimulated by ADP and inhibited by ATP and NADH. This reaction produces
NADH and CO2.
Pyruvate carboxylase (choice D) is a mitochondrial enzyme that converts pyruvate to oxaloacetate. It
is important in gluconeogenesis and replenishes the oxaloacetate in the citric acid cycle.

[ArchivalUser]

So we have pyruvate ---Acetyl Coa ---citrate syntatase Citrate .
Well glycolisis from glucos eto pyruvate OCCURS in teh CYTOSOL ISN'T ?
PHOSPHOFRUCTOKINASE -1 is active in the 2(SECOND RAT ELIMITED STEP ) in glycolisis, where F2,6 BP is teh MAIN ALLOSTERIC STMULATPR of glucolysis and CITRATE INHIBIT FFK-1 !!!!!

[ArchivalUser]

Dear Zkadhem THANKS FRO POSTING SUCH IMPORTANT QUESTIONS.i NEE DTHIS ...THANKS AGAIN!!
see you tomorow..I can't wait for your questions...