1) Fraction-I, which is a portion of serum prtoein separated by means of gel filtration using Sephadx G-200, formed a complex of trypsin-protein esterase (TPE) when treated with trypsin and did not lose its enzymatic activity. Mild anti-tryptic activity was also demonstrated in this fraction.
The ratio of the tryptic activity to the anti-tryptic activity was 5. It is considered that the existence of anti-tryptic activity is due to a loss of enzymatic activity caused by the formation of the complex.
2) The esterase activity of α
2M-enzyme complex in serum was studied with the use of α-N-benzoyl-DL-arginine-p-nitroanilid HCl (BAPNA) as the synthesized substrate in human subjects. It was found that the serum protein, which had esterase activity, could be absorbed by anti-α
2M rabbit serum immunochemically. This complex could also protect trypsin esterase activity from soybean trypsin inhibitor. Moreover, our data suggested that one mole of α
2M was bound to two moles o trypsin.
3) In 83 patients with various diseases, the values of serum TPE activity were compared with those of serum α
2M measured by an immunological method. The result, that the correlation coefficient between the two values was 0.95 showed the greatly significant relation of TPE activity to α
2M level in serum. Accordingly, the measurement of α
2M concentration in serum can be replaced by the determination of serum TPE activity, which is a simpler technique.
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