In this study, we report that the recombinant $alpha$ subunit chaperonin protein (ApCpnA) from Aeropyrum pernix K1 can efficiently prevent the thermal aggregation and inactivation of foreign model proteins, such as citrate synthase (CS) from porcine heart, alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae(four 37.5 kDa subunits), and malate dehydrogenase (MDH) from Thermus flavus(two 67 kDa subunits). In the presence of ApCpnA and ATP, the thermal aggregation of CS and ADH were prevented by 90 and 65%, respectively, at each 43 and $50^{circ}C$. Also, the activities of CS, ADH, and MDH under the thermal inactivation conditions were stably maintained at higher than 80% by addition of ApCpnA and ATP, while the activities of those enzymes in the absence of ApCpnA and ATP were dramatically inactivated and decreased below 20% within 30 min. Based on these results, we propose that the $alpha$ subunit chaperonin from the hyperthermophilic archaeon, A. pernix K1 can be utilized to enhance the durability and cost effectiveness of high-temperature biocatalysts.