Why is water excluded from the active site of phosphorylase?...

Key Concepts

Enzyme Active Site

The active site of an enzyme is the specific region where substrate molecules bind and undergo a chemical reaction. Its microenvironment is optimized (for example, by being hydrophobic or excluding water) to facilitate the proper orientation and reactivity of substrates during catalysis.

Water Exclusion in Enzymatic Reactions

Excluding water from the active site is a strategy used by enzymes to prevent side reactions such as hydrolysis. In reactions where a specific nucleophile is required, like the incorporation of phosphate in phosphorylase-catalyzed reactions, preventing water from entering ensures that the intended chemical process proceeds efficiently.

Phosphorolysis Reaction Mechanism

Phosphorylase enzymes catalyze phosphorolysis, which involves the addition of inorganic phosphate to cleave a bond in the substrate. This mechanism relies on the preferential binding of phosphate over water, and the active site is adapted to favor this reaction pathway while minimizing competing reactions that involve water.

Mutation Impact on Enzyme Function

Mutations that alter the structure of the enzyme's active site can disrupt its finely tuned microenvironment. If a mutation permits water to enter the active site, it can lead to undesirable hydrolysis reactions, reducing the specificity and efficiency of the enzyme's normal phosphorolysis activity.

Transcript

00:01 Hello there, students.

00:01 Today, we're going to be discussing more about this question in regards to the chapter on glycong metabolism.

00:12 And with a question they asked, why is water excluded from the active side of, sorry, if i mispronounce this word, phospholase? well the reason behind that when phospholus is that it wants to prevent hydrolysis and by preventing water from entering because if the water does enter it leads to formation of glucose rather than glucose 1 phosphate so more about hydrolysis.

00:52 Hydrolysis is just where you cut with water.

00:56 So the formula you see right here, what happens when you have this chemical component out of water and all it does just separates.

01:05 That formation.

01:07 An example i can show is with glycong when you add water, even those being catalyzed by alpha -16 glucositis, you do see the same effect happens where yes, you have the separation and that you have the separation of that chemical component and you see that little that part with the r is on that side and yeah.

01:42 So more to add in, like they want us to predict what happens if a mutation happened, that leads to hydrolysis to occur or water entering into the molecules to cut or slice the molecule component.

02:01 Let's bring up like a site mutinich experiment where let's say it was going on in the phosphorylas where where tri -573 is a hydrogen bond to the 29 -0 -hydrogen group.

02:28 I mean, no, my bad.

02:31 I mean, hydroxyl group, my bad, of a glucose residue.

02:38 And the ratio of glucose 1 -phosphate to glucose product is, like, 9 ,001 for the wild type ancine to 501 for the pag 573.

02:58 What happens there is that at least like the water molecules will occupy the sites that are normally filled by fentanyl hydroxyl group of tyrosin, that that's what.

03:18 I was trying to say...

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