Spaltung des α-L-Arabinofuranosids, β-D-Glucopyranosids und β-Cellobiosids von 4-Nitrophenol durch Enzyme verschiedener Pilze - ein Beitrag in Verbindung mit Versuchen zur Steigerung der Selektivität der Tumortherapie

To carry out long-term experiments as part of a therapy concept of malignant tumours using inactive transport forms of cancerostatic substances and their specific cleavage in the acidic pH region of the tumours by application of extraneous enzymes, we require enzymes with similar catalytic and pharmacokinetic properties which differ from each other in immunological respect. In the search for such enzymes, the α-L-arabinofuranosidases from 12 different fungi, among them 9 basidiomycetes, were studied. The enzymes mentioned were demonstrable in all fungi. Optimum pH values ranged between 2.5 and 5.5. The Km values for the cleavage of α-L-arabinofuranoside were, in most cases, 0.5 to 1.8 moles · liter−1 · 10−3. With regard to pH dependence, the α-L-arabino-furanosidases of most of the fungi investigated proved adequate for the long-term trials envisaged. 4-nitrophenyl-β-D-glucopyranoside and -β-cellobioside were also cleaved by enzyme preparations of all the 11 fungi investigated. The β-D-glucopyranosidases showed a less favourable pH dependence than the α-L-arabinofuranosidases. The cleavage of 4-nitrophenyl-β-cellobioside, on the contrary, showed mostly a comparatively favourable pH dependence. On the basis of the coinciding optimal pH values and the occurrence of 4-nitrophenyl-β-D-glucopyranoside as an intermediate product in the cleavage of the corresponding cellobioside, we assume that both substrates are cleaved by β-glucosidase. Because the occurrence of the glucoside during the cleavage of cellobioside is undesirable for the therapeutic trial, a method is proposed for selection of an appropriate cellobioside splitting enzyme basing on the present studies and the relevant literature.