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Altered phosphorylation state of branched‐chain 2‐Oxo acid dehydrogenase in a branched‐chain acyltransferase deficient human fibroblast cell line
Author(s) -
Eisenstein R. S.,
Hoganson G.,
Miller R. H.,
Harper A. E.
Publication year - 1991
Publication title -
journal of inherited metabolic disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 102
eISSN - 1573-2665
pISSN - 0141-8955
DOI - 10.1007/bf01804386
Subject(s) - biochemistry , maple syrup urine disease , fibroblast , dihydrolipoamide dehydrogenase , phosphorylation , mitochondrion , biology , dehydrogenase , protein subunit , branched chain alpha keto acid dehydrogenase complex , microbiology and biotechnology , acyltransferase , chemistry , enzyme , amino acid , leucine , gene , in vitro
Summary The abundance and phosphorylation state of the polypeptide constitutents of the human branched‐chain 2‐oxo acid dehydrogenase complex were examined in mitochondria from normal and maple syrup urine disease (MSUD) fibroblasts. In normal fibroblast mitochondria two forms of the E 1α subunit were observed: non‐phosphorylated (E 1α ) and phosphorylated (E 1α−P ). About 40–50% of E 1α was present as E 1α−P . The ability to quantitate the two forms of E 1α permitted examination of the association between decreased capacity to oxidize branched‐chain 2‐oxo acids and the phosphorylation state of E 1α . Changes in phosphorylation state of E 1α were observed in MSUD fibroblasts as compared to control cells. Of particular interest was the absence of E 1α−P in an MSUD fibroblast line which lacked the dihydrolipoyl acyltransferase (E 2 ) subunit of the dehydrogenase complex. In two MSUD cell lines deficient in E 1α , the abundance of E 1α−P appeared to be preferentially reduced. A fourth MSUD cell line contained normal quantities of E 3 , E 2 and both forms of the E 1α polypeptide. Our results indicate that alterations in the abundance of dehydrogenase complex polypeptides in MSUD fibroblasts may influence the phosphorylation state of the E 1α polypeptide. They demonstrate the potential for examining simultaneously mutations which affect both the catalytic and regulatory components of the dehydrogenase complex.