[NewtoAtoms]

Hello,

I am currently studying glycolysis and have stumbled upon isomerase. 
Can anyone explain the function of isomerase in glycolysis. Why did it rearrange glucose-6-phosphate?
What was the purpose of that?

Can anyone direct me to an internet site of explain this to me?

Would it be safe to say that if isomerase was somehow rendered nonfunctional, it would cancel or harm the output of ATP??

Thank you!!

New to biochemistry

[Padfoot]

Would it be safe to say that if isomerase was somehow rendered nonfunctional, it would cancel or harm the output of ATP??

Yes, inhibition of the enzymes involved in glycolysis is one of the ways in which glycolysis is regulated.  For example pohosphofructokinase, another enzyme in glycoylsis, is allosterically inhibited by ATP which reduces glycolysis in times when levels of ATP in the cell are already high. 

Maybe someone else can help you out with your first question.

[JGK]

Saccharides come in two forms, adoses (contain an aldhyde group) and Ketoses (contain a ketone group).

The Isomerase enzyme can convert an aldose to a ketose (or a ketose to an aldose)

In glycolysis, following the initial phosphorylation of glucose phosphoglucose isomerase converts glucose-6-phosphate (an aldose) to fructose-6-phosphate ( a ketose), in order to permit the second phosphorylation by phosphofructokinase to occur at carbon 1 producing fructose 1, 6 diphosphate. Isomerase converts carbon 1 from a CHO group to CH2OH group.

[victor]

Yup, conversion of glucose-6P into fructose-6P permits the phosphorylation in the C1 because it also change the structure from the pyranose into furanose (where furanose has a -CH2OH group in the anomeric carbon which is ready to undergo phosphorylation).

[SanShouXMA]

Saccharides come in two forms, adoses (contain an aldhyde group) and Ketoses (contain a ketone group).

The Isomerase enzyme can convert an aldose to a ketose (or a ketose to an aldose)

In glycolysis, following the initial phosphorylation of glucose phosphoglucose isomerase converts glucose-6-phosphate (an aldose) to fructose-6-phosphate ( a ketose), in order to permit the second phosphorylation by phosphofructokinase to occur at carbon 1 producing fructose 1, 6 diphosphate. Isomerase converts carbon 1 from a CHO group to CH2OH group.

Sorry to bring this back up. I just discovered this site and think it will be amazingly helpful to me in my classes. 

So let me get this straight. Isomerase's job is to convert Dihydroxyacetone phosphate into Glyceraldehyde-3-phosphate and vice versa to create equilibrium?  But because the next enzyme in Glycolysis requires the use of Glyceraldehyde-3-phosphate equilibrium is never achieved. Am I correct?

[Wreath]

SanShouXMA:
I'm afraid you are messing up with two different isomerases. There is a Glucose-6P isomerase, which converts G6P to Fru-6P. Secondly, there is a triosaphosphate isomerase, which is needed to convert dihydroxyaceton phosphate to glyceraldehyde-3P.

The second isomerase is not needed for maitenance equilibrium between G3P and DHAP, at least no in way you suggested. It is supposed to convert DHAP to G3P only, because
1) there´s 1:1 G3P and DHAP created from Fru-1,6-PP
2) you need ONLY G3P to proceed glycolysis reactions, so the next reaction after creating G3P and DHAP is consuming G3P and DHAP would accumulate. So triosaphosphate isomerase converts DHAP to G3P, which is completely usable for glycolysis. As you can see, there is no reason for triosaphosphate isomerase to convert G3P to DHAP.

But basically, there IS a equilibrium maintenance function, but only the equilibrium means about 90% G3P and 10% DHAP :-)