An
organelle that breaks down the
proteins the
cell doesn't need. It uses
hydrogen peroxide and
catalase to achieve this. Unlike
mitochondria or
chloroplasts it doesn't have any
DNA or any means to
transcribe proteins, so it has to get all its
proteases and so on from the host cell.
It is possible that this is an ancient remnant of a symbiotic bacterium that has gradually lost the ability to look after itself. However, since it has no genetic material, there is no way of looking at its phylogeny to test this. It has been shown, in leaves, that plant glyoxysomes are converted to peroxisomes during greening. Photorespiration is carried out in plant peroxisomes and the necessary enzymes are transported into the organelle. At the same time, the glyoxysomal enzymes are broken down. This suggests that the two distinct organelles are actually different developmental stages of the same microbody; tailored by the cell for separate purposes.