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KMID : 0380219990320060573
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Journal of Biochemistry and Molecular Biology
1999 Volume.32 No. 6 p.573 ~ p.578
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Properties of Trypsin-Mediated Activation of Aspartase from Hafnia alvei
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Lee Min-Sub
Choi Kyoung-Jae
Kwom Si-Joong
Kang In-Sug
Ha Joo-Hun
Kim Sung-Soo
Han Myung-Soo
Yoon Moon-Young
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Abstract
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Treatment of Hafnia alvei aspartase with limited tryptic digestion resulted in a marked increase in enzymatic activity. The activation required a few minutes to attain maximum level and, thereafter, the activity gradually decreased to complete inactivation. The degree of cleavage associated with the activation was extremely small as judged by SDS-PAGE. Upon activation, the optimum pH and temperature were essentially unchanged. When trypsin-activated enzyme was denatured in 4 M guanidine-HCI followed by removal of the denaturant by dilution, the restoration of activity was similar (40%) to that of the native enzyme, indicating a degree of stability. The pKa obtained on the acidic side and the pKb obtained on the basic side of trypsin-activated aspartase were 6.6 and 8.6, respectively, the same as those of the native aspartase, indicating that aspartase may exist in a stable conformation after limited tryptic digestion. These results indicate that the activation of H. alvei may be mediated by a conformational change away from the active site of individual subunits.
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KEYWORD
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Aspartase, Trypsin activation, Hafnia alvei
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