Ornithine decarboxylase from Tetrahymena thermophila: purification, reversible modification and multiple forms

T. thermophila ornithine decarboxylase was purified 1100-fold by an improved procedure to a specific activity of 2.31 x 10(4) nmol/hr/mg protein with a 28% yield. The purified enzyme was a monomer of Mr = 68,000 and had two isoelectric forms with pl's of 5.14 and 5.17 respectively. The Mr = 68,000 enzyme was reversibly modified by a cellular factor of approx. Mr = 10,000 to give rise to two additional forms with decreased DEAE-cellulose affinity.