Year 12s: what will be the first way you research your future options? >>

Glucose-1-phosphate to glycogen + phosphate

We've just done an experiment in a uni module to isolate phosphorylase from potatoes, and then use it in acidic conditions to create phosphate and glycogen from glucose-1-phosphate. We then had to plot the amount of phosphate against time.

I've done that bit, and now I'm onto the part where I need to discuss the shape of my graph and why it's turned out like that.

It goes up, reaches a peak and then levels out over the course of the hour and half during which we took readings of phosphate produced. I know this could be because the enzyme has run out of substrate but I'm sure the lecturer said there were other reasons (he also said no more than one or two sides...I've got a paragraph, so I'm sure there's something else I'm meant to put if he was expecting about page).

So what else could cause the amount of phosphate produced to level out? :confused:

Any help is muchly appreciated. :redface:

Reply 1

jwza

Could the acid denature the phosphorylase?

Reply 2

thegodofgod

Original post by heidigirl

So what else could cause the amount of phosphate produced to level out? :confused:

Any help is muchly appreciated. :redface:

Any other limiting factors you can think of?

Reply 3

Revd. Mike

Original post by jwza

Could the acid denature the phosphorylase?

pH changes don't 'denature' enzymes as such. It causes slight, temporary changes in conformation or binding capacity of the active site and/or substrate, which is reversible.

Also, judging by the fact that the experimental prep specifically used acidic conditions, I'd guess that this enzyme has an optimal pH of <7.

(edited 13 years ago)

Reply 4

DeeWave

Maybe some form of feedback inhibition acting allosterically on the enzyme?

Perhaps depletion of UDP required for the bond formation?

Reply 5

roar558

Original post by Revd. Mike

Don't you mean a pH<7? Though I would agree with the rest of your post. I believe the decrease in phosphate production could be caused by end product inhibition of the enzyme by the phosphate.

Reply 6

Revd. Mike

Original post by roar558

Don't you mean a pH<7? Though I would agree with the rest of your post. I believe the decrease in phosphate production could be caused by end product inhibition of the enzyme by the phosphate.