The kcat for rubisco is 3 sec-1 how long does it takeone
subunit of rubisco to do one reaction.

A subunit of Rubisco takes approximately 0.33 s to perform one reaction

Explanation:

The kcat it's a kinetic first order constant that related the properties of the enzyme substrate complexes in a mechanisms and represents the overall first order process of the transformation of the substrate-enzyme complex into product.

Also kcat can be seen as the turnover number of an enzyme, representing the maximum number of substrate molecules that the enzyme can transform into product per time unit and per active site.

If the kcat is 3 s^-1, it means Rubisco can catalyse the transformation of 3 substrate molecules per second.

So, the time that takes a single reaction, should be the inverse of kcat.

To see it more clearly, the time needed for a single reaction is the time observed divided by the number of reactions done during that time.

In other words:

3 reactions 1 s

1 reaction x

So the time that takes one Rubisco subunit to do one reaction is approximately 0.33 s