Enzymes

The lysosomes are so called because they contain lytic or destructive enzymes. It is probable that the enzymes are stored within the lysosomes in crystalline or semi crystalline form. The enzymes are bounded by a membrane which has a low permeability to the substrates of the enclosed enzymes. The membrane thus protects the cell from autolysis enclosed enzymes. The membrane thus protects the cell from autolysis. Since most of the lysosomal enzymes function better under acidic conditions, they are collectively termed as acid hydrolases.
Lysosomes isolated from one source do not present a homogeneous picture under the electron microscope. This has led to the suggestion that a particular lysosome may contain only a few, or even a single, species of enzymes.

1. Nucleases, which include rib nuclease and deoxyribonuclease, break down polynucleotides into their nitrogenous bases, phosphates and pentose sugar.

2. Phosphatases, e.g. acid phosphate, break down phosphate esters to monophosphates.

3. Lipases act on lipids, breaking them down into fragments.

4. Proteases or proteolytic enzymes hydrolyze proteins and break them down to their constituent amino acids.

5. Glycosidases break down polysaccharides to monosaccharides. They include β-galactosidase, β-glucoronidase, and α-mannosidase which act on polysccharides, and α-glucosidase which acts on α-glucosides (formed from glycogen).

6. Sulphatases act on sulphate esters breaking them down into fragments.
On the death of the cell the lysosomes rupture and release their enzymes which destroy the remnants of the cell. Digestion of foreign material within the cell can also take place by selective release of hydrolytic enzymes from the lysosomes.

The lysosomes can therefore degrade every biological macromolecule. The lysosomes population is heterogeneous. A single lysosome need not contain all the enzymes. Moreover many of the enzymes exist in multiple molecular forms, with distinctive locations in different parts of the cell, tissue of organism.