Protein carboxylmethylation in porcine spleen is mainly mediated by class I protein carboxyl O-methyltransferase.
The functional role of protein carboxylmethylation (PCM) has not yet been clearly elucidated in the tissue level. The biochemical feature of PCM in porcine spleen was therefore studied by investigating the methyl accepting capacity (MAC) of natural endogenous substrate proteins for protein carboxyl O-methyltransferase (PCMT) in various conditions. Strong acidic and alkaline-conditioned (at pH 11.0) analyses of the MAC indicated that approximately 65% of total protein methylation seemed to be mediated by spleen PCMT. The hydrolytic kinetics of the PCM products, such as carboxylmethylesters (CMEs), under mild alkaline conditions revealed that there may be three different kinds of CMEs [displaying half-times (T1/2) of 1.1 min (82.7% of total CMEs), 13.9 min (4.6%), and 478.0 min (12.7%)], assuming that the majority of CME is base-labile and may be catalyzed by class I PCMT. In agreement with these results, several natural endogenous substrate proteins (14, 31 and 86 kDa) were identified strikingly by acidic-conditioned electrophoresis, and their MAC was lost upon alkaline conditions. On the other hand, other proteins (23 and 62 kDa) weakly appeared under alkaline conditions, indicating that PCM mediated by class II or III PCMT may be a minor reaction. The MAC of an isolated endogenous substrate protein (23-kDa) was also detected upon acidic-conditioned electrophoresis. Therefore, our data suggest that most spleen PCM may be catalyzed by class I PCMT, which participates in repairing aged proteins.
Cho
Jae Youl
JY
Department of Genetic Engineering, Faculty of Life Science and Technology, Sungkyunkwan University, Suwon 440-746, Korea.
Kim
Sung Soo
SS
Kwon
Myung Hee
MH
Kim
Seong Hwan
SH
Lee
Hyang Woo
HW
Hong
Sungyoul
S
D000818:Animals; D002848:Chromatography, DEAE-Cellulose; D002851:Chromatography, High Pressure Liquid; D004058:Diffusion; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D008745:Methylation; D011497:Protein O-Methyltransferase / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D013154:Spleen / Q000378:metabolism*; D013347:Subcellular Fractions / Q000201:enzymology; D013552:Swine
D011506:Proteins; D011497:Protein O-Methyltransferase; D010450:Endopeptidases