Enzymes of the 3-Oxoadipate Pathway in Fungi: A Serological Study of 3-Carboxymuconate Cyclase (Lactonizing Enzyme) in Fungi and its Possible Taxonomic Significance

Abstract

The immunoglobulin fraction of antiserum prepared against a homogeneous preparation of 3-carboxymuconate cyclase from Aspergillus niger ~6 was used to study the serological relatedness of the enzyme in crude extracts of other fungi. l'mmunodiffusion and immunoelectrophoresis experiments confirmed the homogeneity of the pure A . niger ~6 cyclase, its serological identity with the same enzyme in other strains of A . niger and the complete absence of any cross-reaction with the analogous 3-carboxymuconate cycloisomerase from Pseudomonas putida and Nocardia opaca. Extensive cross-reactions were observed with the cyclases from other species of Aspergillus and Penicillium. When such cross-reactions were examined quantitatively by the precipitin technique, several genera believed to be taxonomically related to Aspergillus and Penicillium on morphological grounds showed crossreacting cyclases. Within the genera there was a broad correlation of serological relationships with morphological subdivisions. These correlations were considerably better than can be achieved by determinations of DNA base compositions because most of the genera examined have GC ratios of 50 to 55 mol %. Crude extracts of two taxonomically unrelated Basidiomycetes showed no serological relatedness to the antisera.