Organization of Polyaromatic Biosynthetic Enzymes in a Variety of Photosynthetic Organisms

Abstract

Sucrose density gradient centrifugation was used to estimate the molecular weights and determine possible physical aggregation of the enzymes catalyzing steps 2 to 6 in pre-chorismic acid polyaromatic biosynthesis in Anabaena variabilis, Chlamydomonas reinhardi, Euglena gracilis, Nicotiana tabacum , and Physcomitrella patens . In A. variabilis , the five enzymes are separable. Similar results were obtained for P. patens, N. tabacum , and C. reinhardi extracts, except that dehydroshikimate reductase and dehydroquinase were not separable by this method. Evidence is presented for an enzyme aggregate containing five activities, with a molecular weight of approximately 120,000 in E. gracilis; dissociation of this aggregate into components corresponding to molecular weight of ca. 60,000 is also observed. Preliminary evidence concerning the enzymatic composition of the 60,000-molecular-weight components is presented and discussed. Similarities between the E. gracilis polyaromatic aggregate and that of Neurospora crassa are discussed.