The enzyme which catalyses the conversion of proteins to amino acids is protease.

Proteins are large biological molecules made up of amino acids. They perform a variety of functions in the body, including serving as structural components, enzymes, hormones, and antibodies. In order for proteins to be utilized by the body, they need to be broken down into their constituent amino acids. This breakdown process is catalyzed by a class of enzymes called proteases.

Protease:
Proteases are enzymes that cleave peptide bonds between amino acids in proteins. They play a critical role in the digestion of dietary proteins in the gastrointestinal tract. Proteases are also involved in various other biological processes, such as protein turnover, regulation of cellular signaling pathways, and immune responses.

Mechanism of Action:
Proteases work by hydrolyzing the peptide bonds in proteins, which results in the release of individual amino acids. The hydrolysis reaction involves the addition of a water molecule to the peptide bond, resulting in the cleavage of the bond and the formation of two separate amino acids.

Types of Proteases:
There are several types of proteases, each with its own specific substrate specificity and catalytic mechanism. Some common types of proteases include:
1. Serine proteases: These enzymes contain a serine residue in their active site that acts as a nucleophile to attack the peptide bond.
2. Cysteine proteases: These enzymes contain a cysteine residue that acts as a nucleophile.
3. Aspartic proteases: These enzymes have an aspartic acid residue in their active site that acts as a nucleophile.
4. Metalloproteases: These enzymes require a metal ion, such as zinc, for their catalytic activity.

Importance:
The conversion of proteins to amino acids by proteases is essential for the body to obtain the necessary building blocks for the synthesis of new proteins. Additionally, proteases play a crucial role in the regulation of various biological processes by controlling the levels and activities of specific proteins.

In conclusion, the enzyme that catalyzes the conversion of proteins to amino acids is protease. Proteases are a diverse group of enzymes that hydrolyze peptide bonds, breaking down proteins into their constituent amino acids. This process is essential for the digestion and utilization of dietary proteins, as well as for the regulation of various cellular processes.