6.2. (Very) Brief Overview of Terminology and Non-Enzymatic Uses of Proteins

The distinction between a “protein” and “peptide” (amino acid polymer) is slightly arbitrary/ambiguous. In general, the term “protein” is used when discussing the fully folded three-dimensional structure (i.e. the tertiary/quaternary structure). However, this is only a (loose) convention and some sources may refer to these structures using different terminology. This text will use “protein” to mean “the tertiary/quaternary structure of one or more peptide polymers”.

Although not the focus of this text, it is important to recognize that proteins are a complex class of compounds that can perform a wide array of functions. This text will focus on the use of proteins as enzymes (catalysts) but a large number of proteins serve other cellular roles. For example, structural proteins such as tubulin can combine to form large assemblies (microtubules) that help with cellular shape, cell division, etc. (Figure 6.4). Other proteins help transport compounds across cell membranes, facilitate communication between cells, etc.

Figure 6.4 – Microtubule Polymer of Tubulin Proteins.

These types of proteins serve important biological functions but are not routinely part of chemical reactions. As a result, they are typically explored in biochemistry courses rather than in bioorganic chemistry.