Iv Symposium “ Plant Peroxidases : Biochemistry and Physiology ” ( Vienna , Austria , July 6 – 10 , 1996 )

The IV Symposium on plant peroxidase (PO) was excellently organized by R. Ebermann, C. Obinger and coll. from the Institute of Chemistry in the Agricultural University, Vienna. It took its sources from an 11-year-old tradition, namely the I Symposium organized by H. in all these events the support of the Geneva University is to be underlined. Some 150 communications (oral presentations and posters) were presented by about 170 researchers from 34 countries; two representatives from Bulgaria (N. Bakardjieva and A. Edreva) were invited. It was fascinating that most of the contributions resulted from the joint efforts of international research groups. University of Geneva, 1996) involve a selection of 70 contributions. The main topics were: structure; enzymology; ascorbate peroxidase; genetics; plant development ; stress and disease; applications. The opening session accentuated on enzyme structure as the most fundamental aspect of PO research. Previously (in 1993) plant POs were defined as a superfamily divided into three classes which show less than 20% similarity: the class I appears to be of prokaryotic origin; class II comprises extracellular fungal PO, and class III – the plant secretory PO (Welinder and coll., Denmark). As stated by Veitch, Smith and coll. (England), " the recent publication of the first three-dimensional structure of a plant peroxidase heralds something of a turning point in the study of these enzymes ". Since the last PO meeting a large number of new per-oxidase crystal structures have been solved including peanut PO (Schuller and coll., USA, Canada, England), horseradish peroxidase C (HRPC) (Gajhede and coll., Denmark, USA, England), and barley PO (Henriksen and coll., Denmark). It was established that the peanut PO is a trimetal glyco protein containing 1 mole Fe, 2 moles Ca and 1 mole Mn per 1 mole protein, and 3 glycan chains, Ca being essential for the enzyme activity; its loss causes con-formational changes at and around the active site and the heme. Mn was not expected to occur in higher plant PO (Van Huystee and coll., Canada). The solution of the crystal structure of cytochrome C PO (class I) from the bacterium Pseudomonas aeruginosa reveals the existence of a new class, di-heme PO. The single BULG.