02286nas a2200193   4500008004100000245009100041210006900132300001100201490000700212520140500219653025701624653001201881100001501893700001501908700001901923700002701942700001701969856010601986       2002                        eng d00aCalnexin overexpression increases manganese peroxidase production in Aspergillus niger0 aCalnexin overexpression increases manganese peroxidase productio  a846-510 v683 aHeme-containing peroxidases from white rot basidiomycetes, in contrast to most proteins of fungal origin, are poorly produced in industrial filamentous fungal strains. Factors limiting peroxidase production are believed to operate at the posttranslational level. In particular, insufficient availability of the prosthetic group which is required for peroxidase biosynthesis has been proposed to be an important bottleneck. In this work, we analyzed the role of two components of the secretion pathway, the chaperones calnexin and binding protein (BiP), in the production of a fungal peroxidase. Expression of the Phanerochaete chrysosporium manganese peroxidase (MnP) in Aspergillus niger resulted in an increase in the expression level of the clxA and bipA genes. In a heme-supplemented medium, where MnP was shown to be overproduced to higher levels, induction of clxA and bipA was also higher. Overexpression of these two chaperones in an MnP-producing strain was analyzed for its effect on MnP production. Whereas bipA overexpression seriously reduced MnP production, overexpression of calnexin resulted in a four- to fivefold increase in the extracellular MnP levels. However, when additional heme was provided in the culture medium, calnexin overexpression had no synergistic effect on MnP production. The possible function of these two chaperones in MnP maturation and production is discussed.10aAspergillus niger/*enzymology/genetics Calcium-Binding Proteins/*metabolism Calnexin Culture Media *Fungal Proteins HSP70 Heat-Shock Proteins/metabolism Heme/metabolism Peroxidases/*biosynthesis/genetics Phanerochaete/enzymology/genetics Transformation10aGenetic1 aConesa, A.1 aJeenes, D.1 aArcher, D., B.1 avan den Hondel, C., A.1 aPunt, P., J.  uhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11823227