[aj3537]

Can someone please tell or send me something that explains what these mutations do. If I understood the effect of the mutations, I can probably answer the Km and Kcat part of the question.

In referance to Phosphoglycerate mutase, how does H8A, H8S, K59A, and H181E effect Km, Kcat, and why?  Or at least tell me what the letter at the end stands for.

Christina

[Yggdrasil]

H8A means mutation of histidine 8 to an alanine residue.  In other words the first letter and number represent the original amino acid and its position in the polypeptide chain while the final letter represents the amino acid present in the mutant.  (for a list of the one-letter abbreviations of amino acids, see http://en.wikipedia.org/wiki/List_of_standard_amino_acids)

[Arkcon]

Histidine and lysine have very different side chains, and so a substitution can give the polypeptide very different properties.  Histidine is a pretty special amino acid, it is commonly found in the active site of an enzyme -- aj3537: do you know of a specific chemical property of this amino acid's side chain that could account for this?

[aj3537]

Thank you. I know what the function of H and K are in the enzyme I had to draw out the complete mechanism. It would have been easier if the question had just been worded better, such as swap H with A and S. What is the effect on the enzyme. Thanks again.

[Arkcon]

Thank you. I know what the function of H and K are in the enzyme I had to draw out the complete mechanism.

Yes, my biochem teacher said histidine was his favorite amino acid, the imidiazole ring has a pKa close to human physiological pH -- even slight changes in it's local environment can cause it to protonate or de-protonate, and work as a catalyst.

[victor]

I can say that the change from His (an amino acid which commonly at the core enzyme) into another amino acid such as Glu, Ala, and Ser may affect the hydrophobic pocket which is formed at the core enzyme. As we can see that Glu and Ser are both negatively charged and polar amino acid respectively, so I can say that they'll alter the hydrophobic pocket of the core enzyme which usually acts as an active site. Therefore, it alters the Km and Kcat of the enzyme.