What kind of macromolecules are enzymes

Siebenhaller, J. Natta, C. Lincei 4 , 61 Eklund, H. White, A. New York: McGraw-Hill Volkenstein, M. Article Google Scholar. Hopfield, J. CNRS , 53 Download references. You can also search for this author in PubMed Google Scholar. Reprints and Permissions. Why are enzymes macromolecules?.

Naturwissenschaften 66, — Download citation. Received : 01 February Issue Date : October Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative.

Skip to main content. Search SpringerLink Search. Abstract The possible reasons for the macromolecular nature of enzymes are discussed.

References 1. Dordrecht: Reidel in press 2. Pauling, L. Hammes, G. USA 67 , Google Scholar Shaw, E. B , Google Scholar Philipps, D. New York: Dekker Google Scholar San Francisco: Freeman Google Scholar New York: Wiley Google Scholar Each is an important cell component and performs a wide array of functions. Biological macromolecules are organic, meaning they contain carbon.

In addition, they may contain hydrogen, oxygen, nitrogen, and additional minor elements. Most macromolecules are made from single subunits, or building blocks, called monomers. The monomers combine with each other using covalent bonds to form larger molecules known as polymers. In doing so, monomers release water molecules as byproducts. Figure 1. In the dehydration synthesis reaction depicted above, two molecules of glucose are linked together to form the disaccharide maltose.

In the process, a water molecule is formed. In a dehydration synthesis reaction Figure 1 , the hydrogen of one monomer combines with the hydroxyl group of another monomer, releasing a molecule of water. At the same time, the monomers share electrons and form covalent bonds. As additional monomers join, this chain of repeating monomers forms a polymer.

Different types of monomers can combine in many configurations, giving rise to a diverse group of macromolecules. Even one kind of monomer can combine in a variety of ways to form several different polymers: for example, glucose monomers are the constituents of starch, glycogen, and cellulose.

This cannot be realized by, say, the interaction of the substrate with a simple linear dipeptide catalyst. Now, notice from figure 2 lower panel that the amino acid residues involved in the active site are generally quite apart from each other in the primary structure — as indicated by the number attached to them.

This is an important point: thanks to the dilution in a long, flexible chain, amino acid residues which are far apart in the primary sequence can come close to each other. Thus, this particular three-dimensionality constructs the magic of the active site, which permits the reactions to occur, usually with high speed at room temperature.

The chemists do not always understand the details of the mechanism, but an important, general point, is the following: although the enzyme works — generally — in aqueous environment, the reaction within the active site does not necessarily take place in water.

Actually, as shown in the simple-minded illustration of figure 4, the enzyme by binding the substrate, extracts it from water, and brings it in a very particular local environment, provided with a particular dielectric constant usually lower than in water , which may facilitate reaction.

From here, let us go back to a point made previously on the basis of figure 2, about the fixed spatial conformation of the active site. How is the active site held in that particular spatial form? Not so for a protein in solution: the enzyme conformation is held relatively rigid — the opposite of a random coil — thanks to a long series of intramolecular stabilizing interactions, as in the example shown in figure 5.

Actually, the non-obvious thing is, that only long chains protein or RNA or DNA can assume rigid conformations in solution — just because of the large number of possible intramolecular interactions — while short chains, like a tetra peptide or a tetra nucleotide, may not possess such a conformational rigidity.

Another good reason for being a macromolecule! Now, let us look at a functional macromolecule like an enzyme or a RNA with a space-filling molecular model, as that shown in figure 6: we see in fact that the enzyme molecule is a spatial continuum, there are no hole or discontinuity in the structure. The X-ray protein specialists assert that proteins are tightly packed as good molecular crystals. And this has an important consequence: that every perturbation in any part of the molecule can be transmitted to all parts of the ensemble.

This may induce conformational changes which in turn may facilitate the change into a different biological activity. Binding — a long chain can give rise to a high stability of the enzyme-substrate complex via non-covalent weak interactions.

Stereochemical complementarity — only with a long chain can tortuous walls be built, which permit the good fit of the substrate. Microenvironment — a long chain can create its own environment for the reaction. Forced proximity of active residues — the active residues may be far apart in the primary sequence, which permits a high degree of freedom for the final adjustments required for catalysis. Let us move now away from the active site on the surface of the enzyme.

One could mention additional reasons, such as the multiple binding of more than one substrate e. Could have not been different? Usually, the analysis of this question ends up with the conclusion that yes, nature was right to do the way she did it. But in making this analysis, there is a lot that we are going to learn.