/Why are enzymes so big?

Why are enzymes so big?

[Back to part 1]

PART II

What can we learn more from the asymmetrical energy distribution (see part 1), besides the interesting fact that particles moving at 25 °C do not have enough energy to drive biochemical reactions?  

Life makes a – Maxwell-Boltzmannjump in spring.

Shifting the temperature up and down (left and right in the video) is not a simple linear process. Increasing the temperature leads to a sudden – non linear – increase in hot particles, that have enough energy to participate in chemical reactions and vice versa. This observation aligns with the lively activity we see in nature when temperatures go up a bit in Spring, or when climate researchers warn us that even a small increase in temperature can have a substantial impact on our planet or when we experience a fever, marked by a small change in our bodies temperature. So how do we relate this to bread?

Well, our bread dough is also alive. Gluten and starch form an organ-like texture. In combination with yeast, bacteria and water the dough is transformed into a body that is very sensitive to temperature and biochemical conditions, very similar to the ones governing our own body and all life on our planet. 

Enzymes play a key role in life
Have you ever wondered what Shakespeare’s dreams were made of? From enzymes of course, large molecules that give meaningless molecular vibrations and collisions a dream like direction by transforming them into a chemically “meaningful” bond. Enzymes play a key role in life and it will not surprise you that they also play an important role in the making of bread. Enzymes are relatively large proteins, a kind of ingenious complex machines. They help break and form chemical bonds using very specific binding areas for target molecules.

In line with Sadoways lecture we are interested where these molecular machines get their energy from.

Chemical bonds vary in strength, leading to a variety of strong and weak interactions between atoms. Biochemical reactions include reactions between molecules in which all of these chemical forces play a role.  Apparently enzymes are able to harvest weak aqueous energies and (de)stabilize specific bonds of a target molecule and reduce the so called  activation energy needed to break and make new bonds. This way enzymatic reactions speed up reactions up to a million time faster or more. Without enzymes almost nothing would be happening at room temperature! Enzymes help streamline the transformation process by actually using much lower energies (temperatures, around 2.5 kj/mol, or 1 /40 ev, 25 °C, ) than those mentioned by Sadoway (part 1) to prepare target molecules for their energy demanding transformation, which does involve higher collision energies (+/-100 kj/mol).

The asymmetrical Maxwell-Boltzmann distribution has a particular energy balance, which seems to fit with the biochemical enzymatic reaction path, that involves both low and high interaction energies. Note that too many hot particles (too warm temperatures) would actually overcook life’s delicate thermal balance. Perhaps it’s this delicate equilibrium between many cold and less hot particles that actually allows enzymes to promote life at moderate temperatures.  

Could the form of the Maxwell-Boltzmann distribution at room temperature be the underlying reason why enzymes are so much larger than their substrates at moderate temperatures?

Saldoway asks in the video: “How do you obtain enough energy at room temperature to make all these biochemical reactions possible?” From an energy perspective enzymes might be large because it might help them to harvest the abundant number of weak (cold) energies available in water at moderate temperatures and direct the energy into their active site.  

More about enzymes:

Enzymes play fundamental roles in almost all life processes. They accelerate a great variety of metabolic reactions and control processes such as signaling, energy transduction and the translation of genetic information. The ability of enzymes to catalyze reactions by many orders of magnitude allows cells to carry out reactions that otherwise would not occur on biologically useful time scales (ref). 

It has been suggested that thermophilic or hyperthermophilic (Tm) enzymes have lower catalytic power at a given temperature than the corresponding mesophilic (Ms) enzymes, because the thermophilic enzymes are less flexible.(ref). 

Until the year 2000, we only knew about two forms of catalysts. But then everything changed. Benjamin List and David MacMillan independently reported that you can use small organic molecules to do the same job as big enzymes and metal catalysts in reactions that are precise, cheap, fast and environmentally friendly.” (ref)


Jechiam Gural
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