It depends on some details of your experiment. If you have only one strain of bacteria expressing one beta-lactamase to deal with, you should grown up a large culture and use it a source to purify the enzyme, if you have that capability. It is better to study a purified enzyme than a crude extract.

If you have many strains to deal with, it may be impractical to purify the enzymes from them all. In that case, a simplified extraction procedure may be necessary. For example, multiple freeze-thaws of a washed cell suspension will release some of the enzyme from Gram-negative cells. The supernatant can then be used to measure beta-lactamase activity. To control for the amount of cellular material released, you can perform a protein assay on the supernatant.

If you are using natural bacterial strains, rather than engineered strains that express specific enzymes, your strains may each have multiple beta-lactamases. You can measure the overall nitrocefin hydrolytic activity of such strains, but you can't determine how much of that is due to each of the enzymes. Each enzyme has different nitrocefin hydrolysis kinetics, and some of them don't hydrolyze nitrocefin at all.

NDM-1 is a membrane-bound enzyme, so it will not appear in the freeze-thaw supernatant.

You also have to consider the conditions of the assay. For metallo-beta-lactamases, a small amount of free zinc ion is needed for maximal activity, and you can't use phosphate buffer because zinc phosphate is insoluble. For most class D (OXA) enzymes, bicarbonate is required.

I would like to know how to prepare nitrocefin standard curve to calculate beta lactamase inhibition. Could you please let me know whether to use nitrocefin (different concentrations) and enzyme for standard curve or any other protocol need to follow.

https://www.researchgate.net/post/How_to_prepare_the_Nitrocefin_standard_curve_for_beta_lactamase_inhibition_assay