By Vidhi Chauhan | 5 September 2024
Without enzymes, biochemical reactions would simply not occur fast enough for life to exist. Enzymes are what allow life to be as feasible as it is today. /p>
Enzymes are catalysts that work in biological systems. Catalysts are substances that speed up reactions by lowering their activation energy (energy that a reactant must possess for the reaction to proceed). Enzymes speed up biochemical reactions. They are mostly proteins, but some RNA also show catalytic capacity — these are called ribozymes.
How do enzymes work? The essence lies in the structure of each enzyme. Every enzyme is shaped to fit a specific reactant of a specific reaction. This reactant is called a substrate. The enzyme then changes the structure of this attached substrate, which changes the pathway of the reaction in a way that activation energy decreases. The earlier consensus was that enzymes have a “lock and key” model – the enzymes are rigid and attach to the substrate like a key fitting in a lock. But 60 years ago, the biochemist Daniel Koshland proposed the “induced fit” model – the enzymes change their shape for better attachment to their respective substrates.
Enzymes work in a very specific pH and temperature range. Any change in the environment can lead to the enzyme becoming denatured – the shape of the enzyme gets distorted, sometimes irreversibly.
The enzymes are classified using a four level classification system. Each enzyme has a code consisting of four numbers separated by periods, each number corresponding to a level in the system. This code is called the Enzyme Commission Number (EC Number). The first level consists of seven major enzyme classes, which are:
An interesting class of enzymes called polymerases help in DNA replication. They are involved in a process called Polymerase Chain Reaction (PCR). They are different from ligases in that they can join two single nucleotides together, while ligases can only join longer polynucleotide strands.