■Tf^r . '•■- 



154 



X 100, where ER^ and ER^ were the activities of COg (1 or 58 atm)-treated 

 PRO stored at time t and the original activity of non-COg-treated PRO, 

 respectively. " ^ 



Results and Discussion 



Effect of CO . (1 atm) on PPG Activity 



Enzyme activity of untreated PRO incubated at 33°, 38°, and 43°C 

 decreased slightly with increased heating times (Figures 33a, 33b, and 

 33c). If the protein molecule absorbs too much thermal energy, the 

 secondary and/or tertiary structure will become disrupted and enzyme will 

 be denatured and lose its catalytic activity (Segel , 1976). PRO (43 ng 

 protein/mL) solutions exposed to CO^ under similar heating conditions 

 dramatically lost their catalytic activities (Figures 33a, 33b, and 33c). 

 Only 1.5% of the original activity remained after PRO was treated with CO^ 

 at 33°C for 30 min (AA^^^^ymin = 0.0009 vs. 0.059) (Figure 33a). For those 

 samples subjected to CO2 at 38° and 43°C, no enzyme activity was detected 

 after 25 and 20 min, respectively (Figures 33b and 33c). The spiny 

 lobster PRO was more vulnerable to CO2 than corn germ peroxidase 

 (Christianson et al., 1984) and nine commercial enzyme preparations 

 including a-amylase, glucoamylase, /3-galactosidase, glucose oxidase, 

 glucose isomerase, lipase, thermolysin, alcohol dehydrogenase, and 



■ 4 \ '; 



catalase (Taniguchi et al . , 1987). • 



