Definitely yes! Michaelis-Menten kinetics was originally inspired by the observation of saturation behavior in heterogeneous catalysis.

Agreed. The reason for this is that catalysis occurs on the surface of the catalyst, and there are a limited number of places on the surface for the substrate to bind. Here is an example:

https://pubs.acs.org/doi/abs/10.1021/ja961806v?journalCode=jacsat

This is a friendly reminder that questions/answers must be professionally formulated.

The Michaelis-Menten reaction rate law is based on the well defined kinetic model of homogeneous reactions. It does not matter whether the reaction is catalyzed by an enzyme or by whatever catalyst.

Dear Bill, " What is the alternative to this behaviour ?" Do your own home work on enzymatic catalysis. Please, always capitalize "michaelis menten"

Dear Armindo. I have never heard that " Michaelis-Menten kinetics was originally inspired by the observation of saturation behavior in heterogeneous catalysis." Please, prove.

Dear Adam, your example

https://pubs.acs.org/doi/abs/10.1021/ja961806v?journalCode=jacsat

has nothing to do with a heterogeneous catalysis.

The M-M equation was formulated for an enzyme-catalyzed reaction many years ago (beginning of the last century). It is worth remembering the assumptions, especially the most important, that S is the substrate controlling the reaction rate. Without this assumption, the equation only applies to the isomerization reaction. There are also several other assumptions. It is also worth remembering that the M-M equation is a special case of the equation of Victor Henri, which took into account not only substrate and product inhibition.

There are equivalents (in the mathematical sense) of the M-M equation. List is long: Monod equation, Langmuir isotherm, L-H equation, hyperbolic equation, favorite, by describing adsorption kinetics, "pseudo-second order model" etc.

Answering the question: The equations similar to M-M may be used to describe the reaction not catalyzed by enzyme but any solid catalyst. This is determined by the result of kinetic studies. The plot will be the same, but its interpretation will be different. Regards,

Dear Yurii,

please read Henri, V., 1903. Lois générales de l'action des diastases. Librairie Scientifique A. Hermann., which as clearly acknowledged in Michaelis, L.; Menten, M.L. (1913). "Die Kinetik der Invertinwirkung". Biochem Z. 49: 333–369 provided the theoretical framework of what came to be known by "Michaelis-Menten kinetics". (Unfortunately, Henri has not controlled pH in his experiments, which left his conclusions on shaky ground. Michaelis and Menten addressed this problem.)

Victor Henri ( the first years of the twentieth century), above all, overtook the descriptions of kinetics of enzymatic reactions for decades. Regards,

Thank you for your help everyone. So can I clarify, do all catalysts exhibit saturation kinetics? I am finding it difficult to find information on this

There is no such thing as saturation kinetics. Saturation is a limit state. You do not need an assumption about the so-called "saturation" to derive the M-M equation This behavior is predicted by the M-M equation, but is not predicted by the Andrews model, or the L-H model for the bimolecular reaction. Regards,

Dear Armindo, please prove that " Michaelis-Menten kinetics was originally inspired by the observation of saturation behavior in heterogeneous catalysis." See Miroslaw's comments to your answer.

The article I cited is called "Saturation Kinetics in Dirhodium(II) Carboxylate-Catalyzed Decompositions of Diazo Compounds." I chose it because it is about organometallic catalysis, which was the original subject of the question. It is not about heterogeneous catalysis, as Yurii pointed out.

Michael's-Menten plot for a non enzyme catalyst look like Straight line having the intercept. This indicates the intermediate complex formation between starting reactants.

Remark 1 (Adam B. Shapiro, PhD)

If someone wants to use the term "saturation kinetics", then of course shi or he can. Personally, I am opposed to creating terms with ambiguous meanings. But if someone likes ....

Remark 2 ( Madhukar Baburao Deshmukh, PhD)

I do not know how to understand the sentece " Michael's-Menten plot ..... intercept.". This is more likely to be associated with the description of the Lineweaver and Burk method. If one literally treat what you wrote, it would mean that for a substrate concentration equal to zero, the reaction rate is greater than zero.

Regards,

Saturation kinetic can be observed in chemical heterogeneous catalysis too when the reaction is slow (small reaction rate): activation + reaction + release of product. Whereas when the rate is fast enough, in my opinion, we can not observe saturation of catalyst.

In chemical heterogeneous catalysis we talk more about cooking or blocking of active sites,

I personally do not advise the using biochemical view and concept in chemistry, we can do a similarity in some cases only.

For example for biochemist TON is equivalent to TOF for chemist. That is not logic at all, TON is turn over number: number has no unit but TOF is the turn over frequency is a rate= TON/time.

It seems to me that for a single chemical reaction (omitting the autocatalytic and strongly inhibided reactions) its rate at the beginning is greater than in the subsequent stages. So the attempt to link the so-called "saturation kinetics" with the rate of chemical reaction is in my opinion unjustified. In addition, regardless of whether we are dealing with an enzyme or with a solid catalyst, there will always be an upper limit of reaction rate. Regards,

Just to clarify a point made by Iyad Karamé, although it is not exactly relevant to the present discussion: In enzymology we speak of turnover number as synonymous with the kinetic constant kcat. It is not unitless. It has units of reciprocal time, and means the number of catalytic cycles per enzyme molecule per unit time at the theoretical maximal rate, i.e. when the enzyme is fully saturated with substrate.

Dear Adan,

Couple corrections to your statement: " turnover number as synonymous with the kinetic constant kcat. "

kcat is synonymous to the TurnOver Frequency (TOF) in catalysis. TurnOver Number (TON) means " the number of catalytic cycles per enzyme (catalyst) molecule"

I fully agree with your definition: kcat " has units of reciprocal time, and means the number of catalytic cycles per enzyme molecule per unit time at the theoretical maximal rate, i.e. when the enzyme is fully saturated with substrate. " I would also add that "kcat= TOF(maximum)

Thanks DR. Yurii V Geletii

Dr . Adam Shapiro , I know that you mean by TON rate and it is not right for us as specialist in catalysis

Kcat is the TOF: turn over frequency which has unit = 1/unit of time

I meant here , that enzymatic catalysis is a very small part of catalysis and we cant generalize your concept to our field

Biochemistry is a part of chemistry and not a basic sciences as chemistry, physics and math,

Again, the "saturation of the enzyme". If we would like to talk about the saturation of the enzyme, it concerns a very short time - a moment. In fact, after exceeding a certain concentration, at given moment, the enzyme is not able to process this excess substrate. And as a result, a further increase in concentration does not increase the rate of reaction. The rate reaches the upper limit - it can be the maximum, but it does not have to. In addition, whether someone uses the term "saturation kinetics" in relation to the formation of saturated vapor? And there it would be more justified. Regards,

I am also wondering why the discussion, initially focused on the behavior of the enzymatic reaction and the reaction in the presence of organometallic catalysts, has departed from this topic. What is TOF, TON and kcat is currently being discussed, although it has already been discussed many times on the RG, and as the consent was not, it is not. Is it possible to reconcile the view of an enzymologist and a specialist in heterogeneous catalysis? - I do not know. But that the mathematical description in both cases is similar, both sides try not to notice. Regards,

Miroslaw, Even an auto catalytic can be modeled as LH inhibited reaction with strong inhibition by one or more of the feed components.

It is easy to prove that at least 90% of most proposed rate expressions are incorrect because at least 10 different expressions are typically proposed for any interesting reaction. Most of the time they are all wrong - but still useful

Well, let's discuss it. Dear Rick, I have not written that auto-catalytic reactions can not be modeled using L-H kinetics. My comment referred only to the first part of Prof Iyad Karame's statement - which I disagree with. In addition, I referred to the rate of a single reaction. If you look at my papers and there are several of them, I used both the power and L-H kinetics to describe the auto-catalytic reaction. These are theoretical works aimed at optimization, from the point of view of grain size distribution in a tubular reactor. Referring to the second part of your statement, I fully agree with it. I will give one example. Once years ago, I was developing kinetic data for N2O synhesis in an aqueous solution. The theory suggested that the best should be the kinetic equation taking into account the inhibition of water. The equation was quite complicated and had several variants. It turned out, however, that a similar mean relative error had the power equation with the exponent between zero and one. Regards,

Miroslaw, I think (as usual) we are in agreement. My point was that it is not always true that the rate at the beginning is greatest - even if the reaction is not autocatalytic and that most "rigorous" rate expression are just sophisticated looking correlations.