DIFFERENCES IN CATALYTIC ACTIVITIES AND SUBUNIT PATTERN OF MULTICATALYTIC PROTEINASE COMPLEXES (PROTEASOMES) ISOLATED FROM BOVINE PITUITARY, LUNG, AND LIVER - CHANGES IN LMP7 AND THE COMPONENT NECESSARY FOR EXPRESSION OF THE CHYMOTRYPSIN-LIKE ACTIVITY

Polyacrylamide gel electrophoresis and high performance liquid chromat ography of multicatalytic proteinase complexes (MPC) isolated from bov ine pituitary, lung and liver showed marked differences in the pattern of subunits, The concentrations of LMP7 in the lung and liver were 10 and 5 times, respectively, greater than those in the pituitary, where as the chymotrypsin-like activity and the amount of a subunit (BO2), n ecessary for its expression, were markedly decreased in the lung and m oderately decreased in the liver, Lower trypsinlike, small neutral ami no acid preferring, and peptidyl-glutamyl-peptide hydrolyzing activiti es were also found in the lung and liver. The activity of the branched chain amino acid preferring component (BrAAP), predominantly latent i n the pituitary, was highly activated in the lung and liver, as eviden ced by a greatly decreased IT, and a 20-fold increase of the specifici ty constant V-max/K-m, indicating facilitated substrate access to its active site and increased affinity toward substrates with branched cha in amino acids in the P-1 position, It is suggested that overexpressio n of LMP7 in the lung is related to increased exposure of the airways to foreign antigens, The possible association between amounts of LMP7 and the activation of the BrAAP component needs further examination.