title: Transport of substrates into peroxisomes: the paradigm of β-lactam biosynthetic intermediates.
abstract: Peroxisomes are ubiquitous organelles that enclose catalases, fatty acid-oxidizing enzymes, and a variety of proteins involved in different cellular processes. Interestingly, the late enzymes involved in penicillin biosynthesis, and the isopenicillin N epimerization enzymes involved in cephalosporin biosynthesis are located inside peroxisomes in the producer fungi Penicillium chrysogenum and Acremonium chrysogenum. Peroxisome proteins are targeted to those organelles by peroxisomal targeting signals located at the C-terminus (PTS1) or near the N-terminal end (PTS2) of those proteins. Peroxisomal membrane proteins (PMPs) are largely recruited by the interaction with specific sequences in the Pex19 protein. The compartmentalization into peroxisomes of several steps of the biosynthesis of penicillin, cephalosporin, and other secondary metabolites raises the question of how the precursors and/or intermediates of the biosynthesis of β-lactam antibiotics are transported into peroxisomes and the mechanisms of secretion of the final products (penicillin or cephalosporin) from peroxisomes to the extracellular medium. Recent advances in peroxisome proteomics, immunoelectron microscopy, and fluorescence labeling have shown that the transport of these intermediates is mediated by membrane proteins of the major facilitator superfamily class (drug/H+ antiporters) containing 12 transmembrane-spanning domains (TMS). In some cases, the transport of the substrates (e.g., fatty acids) or intermediates may be mediated by ATP-binding cassette (ABC) transporters. Knowledge on the transport and secretion mechanisms is of paramount importance to understand the complex mechanisms of cell differentiation and their crosstalk with the biosynthesis of different secondary metabolites that act as biochemical signals between the producer cells and also as communication signals with competing microorganisms (e.g., antimicrobial agents or plant elicitors).
authors.forename: Juan-Francisco
authors.initials: JF
authors.lastname: Martín
authors.forename: Carlos
authors.initials: C
authors.lastname: García-Estrada
authors.forename: Ricardo V
authors.initials: RV
authors.lastname: Ullán
mesh_terms: D000164:Acremonium / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000737:chemistry; D001692:Biological Transport; D002511:Cephalosporins / Q000096:biosynthesis / Q000737:chemistry; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D007769:Lactams / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010406:Penicillins / Q000096:biosynthesis / Q000737:chemistry; D010408:Penicillium chrysogenum / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism*; D020539:Sequence Analysis, Protein
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D007769:Lactams; D010406:Penicillins; C025163:cephalosporin C