TY - JOUR
T1 - Human erythrocyte protein L-isoaspartyl methyltransferase
T2 - Heritability of basal activity and genetic polymorphism for thermal stability
AU - David, Cynthia L.
AU - Szumlanski, Carol L.
AU - DeVry, Christopher G.
AU - Ok Park-Hah, Jeong
AU - Clarke, Steven
AU - Weinshilboum, Richard M.
AU - Aswad, Dana W.
N1 - Funding Information:
1 This research was supported by NIH Grant NS17269 to D. W. Aswad, by NIH Grants RO1 GM28157 and RO1 GM35720 to R. M. Weinshilboum, and by NIH Grant GM26020 to S. Clarke.
PY - 1997/10/15
Y1 - 1997/10/15
N2 - Protein L-isoaspartyl methyltransferase (PIMT) is believed to play an important role in the disposition of age-damaged proteins by catalyzing the repair of abnormal isoaspartyl linkages resulting from the spontaneous deamidation of asparaginyl residues or isomerization of aspartyl residues. As a step toward testing the hypothesis that human disease- or age-related pathology might be associated with a deficiency in PIMT, we investigated basal activity and thermal stability of PIMT in erythrocyte lysates from 299 U.S. family members. Thermal stability was measured because it is a sensitive measure of variation in amino acid sequence. Basal activity was normally distributed with a mean ± SD of 558 ± 43 units/ml erythrocytes. Statistical analysis of the data revealed that basal PIMT activity exhibited a high degree of heritability. Enzyme thermal stability showed a skewed bimodal frequency distribution, and segregation analysis of family member pedigrees was consistent with Mendelian inheritance of two major alleles. No DNA was available from the family samples, so we tested two additional population samples for a known Ile/Val polymorphism at codon 119 and for PIMT activity and thermal stability, using blood donated by 25 Norwegians and by 20 Koreans. Single-stranded conformational polymorphism analysis using polymerase chain reaction revealed a 100% correlation between thermal stability grouping and this polymorphism. The high thermal stability samples were all homozygous Ile, the low thermal stability samples were all homozygous Val, and the intermediate thermal stability samples were all heterozygous. Furthermore, this polymorphism was responsible, in part, for the variation observed in basal erythrocyte PIMT activity. These results will help provide a foundation for future studies aimed at correlating levels of PIMT activity, or other properties of this enzyme, with human disease.
AB - Protein L-isoaspartyl methyltransferase (PIMT) is believed to play an important role in the disposition of age-damaged proteins by catalyzing the repair of abnormal isoaspartyl linkages resulting from the spontaneous deamidation of asparaginyl residues or isomerization of aspartyl residues. As a step toward testing the hypothesis that human disease- or age-related pathology might be associated with a deficiency in PIMT, we investigated basal activity and thermal stability of PIMT in erythrocyte lysates from 299 U.S. family members. Thermal stability was measured because it is a sensitive measure of variation in amino acid sequence. Basal activity was normally distributed with a mean ± SD of 558 ± 43 units/ml erythrocytes. Statistical analysis of the data revealed that basal PIMT activity exhibited a high degree of heritability. Enzyme thermal stability showed a skewed bimodal frequency distribution, and segregation analysis of family member pedigrees was consistent with Mendelian inheritance of two major alleles. No DNA was available from the family samples, so we tested two additional population samples for a known Ile/Val polymorphism at codon 119 and for PIMT activity and thermal stability, using blood donated by 25 Norwegians and by 20 Koreans. Single-stranded conformational polymorphism analysis using polymerase chain reaction revealed a 100% correlation between thermal stability grouping and this polymorphism. The high thermal stability samples were all homozygous Ile, the low thermal stability samples were all homozygous Val, and the intermediate thermal stability samples were all heterozygous. Furthermore, this polymorphism was responsible, in part, for the variation observed in basal erythrocyte PIMT activity. These results will help provide a foundation for future studies aimed at correlating levels of PIMT activity, or other properties of this enzyme, with human disease.
KW - Isoaspartate
KW - Polymorphism
KW - Protein repair
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U2 - 10.1006/abbi.1997.0303
DO - 10.1006/abbi.1997.0303
M3 - Article
C2 - 9343375
AN - SCOPUS:0031572828
SN - 0003-9861
VL - 346
SP - 277
EP - 286
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 2
ER -