Serine protease inactivated by freezing. Why?

Mr. P.A. Sansom psansom at
Wed Feb 15 12:52:01 EST 1995

Hello Peeps!
My monocyte membrane extracts contain a serine protease that loses activity on
freezing at -20C, even though it's very stable at 4C. If the extract is left
at 37C prior to assay, partial activity returns. This leads me to think that
1) the proteinase is a multi-subunit enzyme that breaks up and reforms or
2) an inactive form of the enzyme is converted to the active form at 37C.
The enzyme is inhibited by PMSF but not by trypsin/chymotrypsin inhibitors.

Has anyone experienced anything similar? I would really like to know what
this enzyme is and if this effect has been seen with any other known enzyme
eg elastase, gelatinase-like enzymes.

Thanks in advance

psansom at

Paul A Sansom                                  tel: 081-748-9966 x4208
Department of Biochemistry                     fax: 081-748-5090
The Kennedy Institute of Rheumatology
6 Bute Gardens
London W6 7DW

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