The Discovery of Lysosornes

Lysosomes ("lytic particles") act as the primary component of the intracellular digestive system in virtually all eukaryotic cells, both plant and animal. First recognized biochemically in rat liver, these organelles are membrane-bounded and contain a variety ofdigestive enzymes active at acid pH. Their existence and properties became evident during investigations concerning the latency of the enclosed enzymes . Initially defined by the presence of a single enzyme, acid phosphatase, which liberates inorganic phosphate from a number of monophosphoric esters, lysosomes are now known to contain at least 50 acid hydrolases, including various phosphatases, nucleases, glycosidases, proteases, peptidases, sulfatases, and lipases . Collectively, they are capable of hydrolyzing almost all classes of macromolecules according to the following scheme: