Q.What are the general properties of enzymes?

[!TLDR]

The question asks for the general properties that characterise enzymes as a group.

[!ANSWER]

Enzymes are protein-based biological catalysts that lower the activation energy of specific reactions, act on specific substrates, are not consumed by the reaction and so can be reused repeatedly, and are highly sensitive to conditions such as temperature, pH and substrate concentration.

Enzymes share a characteristic set of properties that follow from their role as biological catalysts. They lower the activation energy needed for their reaction, allowing it to proceed rapidly under the mild temperature and pH conditions found inside a living organism, where the reaction would otherwise be far too slow. They are highly specific, generally acting only on one substrate or a small group of closely related substrates, which is what allows a cell to run many different reactions side by side without them interfering with each other. They are reusable and act catalytically: because an enzyme is released unchanged at the end of the reaction it catalyses, a small amount of enzyme can convert a very large amount of substrate simply by being used again and again, and different enzymes vary enormously in how fast they can do this, a property measured by the turnover number. Finally, enzyme activity is highly sensitive to conditions - it depends on temperature and pH, each of which has an optimum value beyond which activity falls (and, at extremes, the enzyme can be permanently denatured), and it depends on substrate concentration, rising towards a maximum rate (Vmax) as substrate becomes more available, as well as on the presence of co-factors, activators or inhibitors.

[!ANSWER]

So the general properties of enzymes are: they lower activation energy, act with high substrate specificity, are reusable catalysts (not consumed by the reaction), and are strongly sensitive to temperature, pH, substrate concentration and the presence of co-factors or inhibitors.

• Describing enzymes only as 'catalysts that speed up reactions' without mentioning specificity, reusability, or sensitivity to conditions, which are equally central properties.
• Omitting that being unconsumed by the reaction is exactly what makes an enzyme reusable in small amounts.