Determination of kcat from Vmax

Question

[Natasha]

Hello Everyone,

I am trying to convert the value of Vmax to kcat given in this reference: https://www.ncbi.nlm.nih.gov/pubmed/7488210

Vmax value of 1.7nmol/mg/min is given for phosphofructokinase.(in page 901 of the ref.)

When Vmax is multiplied with the molecular weight(82000 g/mol),the resulting value of kcat is in the order of 10^(-9) (units: 1/s)which is too low.

Am I missing something?

Answer 1

[Kevin Blighe]

Don't you have to get your units the same?

82 000 g/mol = 82 000 000 mg/mol = 0.082 mg/nmol

1.7 nmol/mg/min * 0.082 mg/nmol = 0.1394 / min