TY - JOUR
T1 - Enzymatic changes of the bovine pituitary multicatalytic proteinase complex, induced by magnesium ions
AU - Pereira, Maria E.
AU - Yu, Bo
AU - Wilk, Sherwin
N1 - Funding Information:
i This work was supported by Grant 2T32 DA07135-11 (training grant to M.E.P.) from the National Institute on Drug Abuse, NIH Grant NS-17392 (SW.), and ADAMHA Research Scientist Award MH-00350 (S.W.). ‘To whom correspondence should be addressed at Pharmacology Dept., BOX 1215, Mount Sinai School of Medicine of CUNY, One Gustave L. Levy Place, New York, NY 10029.
PY - 1992/4
Y1 - 1992/4
N2 - The effect of magnesium ions on the catalytic activities of the bovine pituitary multicatalytic proteinase complex (MPC) was studied. Mg2+ markedly stimulated the breakdown of dephosphorylated β-casein (caseinolytic activity) and the hydrolysis of CbzLeuLeuGlu-2-naphthylamide (peptidylglutamyl peptide bond hydrolyzing activity) by a 1700-fold purified preparation of MPC. Cleavage of CbzD-AlaLeuArg-2-naphthylamide (trypsin-like activity) was strongly inhibited and cleavage of CbzGlyGlyLeup-nitroanilide (chymotrypsin-like activity) was weakly inhibited. Similar results were produced when enzymatic activities in the absence of Mg2+ were measured at 52 °C rather than at 37 °C. Trace protein impurities were removed by phenyl-Sepharose chromatography. This additional chromatographic step, while not changing the specific activities of hydrolysis of the three synthetic chromogenic substrates, led to a marked activation of the breakdown of dephosphorylated β-casein. Mg2+ was not able to further stimulate the caseinolytic activities of either the phenyl-Sepharose-treated preparation or the preparation measured at 52 °C. Mg2+ therefore converts a "repressed" form of MPC to an "activated" form, possibly by promoting dissociation of a protein inhibitor, and may serve as a physiological regulator of this enzyme complex.
AB - The effect of magnesium ions on the catalytic activities of the bovine pituitary multicatalytic proteinase complex (MPC) was studied. Mg2+ markedly stimulated the breakdown of dephosphorylated β-casein (caseinolytic activity) and the hydrolysis of CbzLeuLeuGlu-2-naphthylamide (peptidylglutamyl peptide bond hydrolyzing activity) by a 1700-fold purified preparation of MPC. Cleavage of CbzD-AlaLeuArg-2-naphthylamide (trypsin-like activity) was strongly inhibited and cleavage of CbzGlyGlyLeup-nitroanilide (chymotrypsin-like activity) was weakly inhibited. Similar results were produced when enzymatic activities in the absence of Mg2+ were measured at 52 °C rather than at 37 °C. Trace protein impurities were removed by phenyl-Sepharose chromatography. This additional chromatographic step, while not changing the specific activities of hydrolysis of the three synthetic chromogenic substrates, led to a marked activation of the breakdown of dephosphorylated β-casein. Mg2+ was not able to further stimulate the caseinolytic activities of either the phenyl-Sepharose-treated preparation or the preparation measured at 52 °C. Mg2+ therefore converts a "repressed" form of MPC to an "activated" form, possibly by promoting dissociation of a protein inhibitor, and may serve as a physiological regulator of this enzyme complex.
UR - http://www.scopus.com/inward/record.url?scp=0026538022&partnerID=8YFLogxK
U2 - 10.1016/0003-9861(92)90128-J
DO - 10.1016/0003-9861(92)90128-J
M3 - Article
C2 - 1550335
AN - SCOPUS:0026538022
SN - 0003-9861
VL - 294
SP - 1
EP - 8
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 1
ER -