Protein Import into Peroxisomes: An Exception to the Rule?

From today's perspective, it seems surprising that peroxisomes were regarded as uninteresting organelles for almost two decades after their discovery in 1954 (Rhodin 1954). Only after the elucidation of the peroxisomal β-oxidation pathway in rat liver (Lazarow and De Duve 1976; Lazarow 1978) and the recognition of peroxisomal disorders in humans (for review, see Van den Bosch et al. 1992; Moser 1993) did it become clear that these ubiquitous eukaryotic cell structures fulfill important metabolic functions. The delay in acceptance of peroxisomes as more than “fossil organelles” was due in part to the fact that, in contrast to most other organelles, peroxisomes lack a general unifying metabolic function. This apparent shortcoming is actually an indication of their specific metabolic role. Because a multiplicity of biochemical functions are now known to reside in these organelles, peroxisomes can be appropriately described as “ulti-purpose” organelles (Opperdoes 1988). The large number of biochemical reactions...