Acta Biologica Tomus XXX. Fasciculi 1-4. [antikvár]

Acta Biol. Szeged. 30, pp. 3-10 (1984) ISOLATION AND CHARACTERIZATION OF THERMOSTABLE ALDOLASE FROM A FACULTATIVE THERMOPHILIC BACTERIUM Magdolna ÁbrahAm and L. Boross Department of Biochemistry, Attila József University, Szeged (Received June 30, 1983) Abstract The aldolase of a facultative thermophilic bacterium, Bacillus sp. was characterized. The stability of the enzyme was compared with those of E. coli aldolase and rabbit muscle aldolase. The thermophilic enzyme belongs to class II of D-fructose-1.6-diphosphate aldolases. The thermophilic aldolase proved to be more stable than the mesophile. The substrate and 2-mercaptoethanol increased the stability of the thermophilic aldolase. Key words: Thermostable, aldolase, characterization. Introduction Microorganisms growing at elevated temperatures possess a higher intrinsic thermostabihty than their mesophilic counterparts. There are several explanations for the thermostability of proteins. The theory of transferable protective factors (Koffler, 1957) has no experimental basis. Amelunxen and Lins (1968) verified the absence of stabilizing or labilizing factors. In vivo studies have revealed that the thermostability of some enzymes may stem from the interactions of the cellular components (Hachimori et al., 1974; Wedler and Hoffmann, 1974). Cofactors, substrates and monovalent or divalent ions may result in intracellular thermostability. According to other results, the reason for the thermostability may be the types and number of stabilizing forces such as H-bonds, apolar and ionic interactions operating in the enzyme molecule (Cass and Stellwagen, 1975; Brandts, 1967). Thermophilic aldolase from Bacillus stearothermophilus has been investigated by Jack and Harris (1975). It is a dimeric Zn^+'Containing enzyme, with a half-life of about 30 min at 337 K. A gradual loss of activity was observed during the isolation, which could be prevented by adding Co^"*" ion to the buffers. The Co^'*'-enzyme cannot be inactivated to any detectable extent during 80 min at 3 37 K. Our study serves the comparative investigations between the aldolase of a facultative thermophile. Bacillus sp. JB-1 and two diflFerent types of mesophilic aldolases. The mesophilic enzymes were purified from E. coll and rabbit muscle, respectively. The thermophilic aldolase was characterized and the thermal stabilities of the three aldolases and the effects of various cations and substrate on the thermal stability were investigated.