I came across the following sentence while reading the paper:
Nanchen, Annik, et al. "Cyclic AMP-dependent catabolite repression is the dominant control mechanism of metabolic fluxes under glucose limitation in Escherichia coli." Journal of bacteriology 190.7 (2008): 2323-2330.
These in vivo flux data are qualitatively corroborated by in vitro enzyme activities in the Crp and Cya mutants, which exhibited significantly reduced activity of the key glyoxylate shunt key enzyme isocitrate lyase ...
My understanding of in vitro experiments is: those performed in artificial set up , possibly only with part of the cell, where the complete cell is not potentially alive. For, example we can test the inhibition activity of a particular enzyme by a metabolite.
In the paper cited, experiments from which flux are derived (chemostat) are considered in vivo. What would it mean to say the enzyme activity was tested in vitro on the mutant? When we say the response of the a single gene knock out mutant, the cell should be intact except for lacing one gene, which would mean that the response is in vivo.
Please help me if I am misunderstanding some thing.