Depends on what your needs and applications for the enzym are - if you are using the enzyme in an analytical /diagnostic setting to quantitate a substrate, you want to go for a low Km to ensure that at low substrate concentration, you are still working at close to Vmax.

If you are using the enzyme in a production setting, where the substrate concentration reliably is very high, you can get away with a much higher Km, as long as it is still well below the substrate concentrations you are working at.

Hi there,

To give answers to your 2 questions:

Is there any relationship between binding affinity to the substrate (Km) and maximum reaction rate (Vmax)?

The only relation between Km and Vm stands in the MM equation: Vm is reached (or rather approached) when [S]0>>Km (at least one order of magnitude between the 2), but the numerical value of Km has no impact whatsoever on the numerical value of kcat .

Does a higher maximum reaction rate (Vmax) come along with a better binding affinity to the substrate (Km)?

No as for instance perfect enzymes (exhibiting the highest possible specificity) have very different sets of Km and Vm (see the link below)

https://slideplayer.com/slide/9392189/28/images/26/Catalytic+Efficiency+%28kcat%2FKM+%29.jpg

Dear Annemarie Honegger Thank you for your good explanation All my best

Dear Dominique Liger Thanks a lot for your reply. I would be grateful if you could tell me some further information. I work on nanomaterials with enzyme-like characteristics (nanozyme). To synthesis of high-performance nanozyme, kcat/Km is more important than Km and Vmax? If so, how can I calculate it?

See https://bio.libretexts.org/Bookshelves/Biochemistry/Book%3A_Biochemistry_Online_(Jakubowski)/06%3A_TRANSPORT_AND_KINETICS/6B%3A_Kinetics_of_Simple_and_Enzyme-Catalyzed_Reactions/B7._Meaning_of_Kinetic_Constants

"Km: The Michaelis constant with units of molarity (M), is operationally defined as the substrate concentration at which the initial velocity is half of Vmax. It is equal to the dissociation constant of E and S only in if E, S and ES are in rapid equilibrium. It can be thought of as an "effective" Kd in other cases.

kcat: The catalytic rate constants, with units of s-1 is often called the turnover number. It is a measure of how many bound substrate molecules turnover or form product in 1 second. This is evident from equation v0 = kcat[ES]

kcat/Km: Under condition when [S]

Hi again kcat/Km is the compromise between catalysis (kcat) and apparent affinity (Km) and is more informative than any of the 2 alone. As Annemarie mentioned, it depends on what you are looking for. For instance if you can provide loads of substrate then you don't really care about the Km, but if the transformation is limiting for dowstream applications then high kcat is preferable to accelerate the production... But I can't say knowing nothing of your project.

Thanks a lot Dominique Liger and Annemarie Honegger

I currently work on the synthesis of high-performance nanozymes and the study of their analytical applications for H2O2 or L-cysteine or even other analyte detection. So smaller Km is more important than Vmax and Kcat. Isn't it?

The Km is limiting for the sensitivity of your assay. For quantitative detection, you want to work under conditions of substrate saturation (Vmax), your Km should be significantly lower than the substrate concentration you wish to determine.

Are you aiming at transforming the totality of the sample content (so working at high enzyme concentration in order to accelerate the process) or aiming at working in steady state condition and deducing the concentration from the initial velocity measurement (which means Km and Vm are known)?

Hi everybody,

I prepared five nanoparticles (NPs) with enzyme-like activity. The catalytic activity was enhanced directly with the increasing content of NPs at a constant concentration of substrates but the high content of NPs use, the low dispersed solution has.

The kinetic of catalytic activity of NPs toward related substrates were investigated. I have 5 Km(s) and 5 Vmax(s).

All I want is to have higher linear range and smaller detection limit (LOD) for H2O2 detection.

As I see I should select NPs with smaller Km.

Combination of both parameters will contribute to lower LOD: higher kcat and smaller Km.

Hi

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

Thanks, the answers of this question are also really helpful.