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Deimination of Human Myelin Basic Protein by a Peptidylarginine Deiminase from Bovine Brain
Author(s) -
Lamensa John W. E.,
Moscarello Mario A.
Publication year - 1993
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1993.tb03612.x
Subject(s) - citrullination , chemistry , myelin basic protein , enzyme , arginine , biochemistry , mole , amino acid , stereochemistry , myelin , citrulline , biology , endocrinology , central nervous system
A peptidylarginine deiminase (PAD; EC 3.5.3.15) has been isolated from bovine brain and some of its characteristics have been studied. The enzyme showed an absolute requirement for Ca 2+ , a temperature optimum at ∼50°C, and two K m values when benzoylarginine ethyl ester was used as substrate, 0.78 mM and 11.2 mM. The higher K m has not been reported previously. Protein substrates for the enzyme included polyarginine and myelin basic protein but not histones. Because one of the components of MBP contains six citrullinyl residues per mole, enzymic deimination appeared to be a likely mechanism. When the most cationic component (C‐1) was subjected to PAD in solution, 17 of the 19 arginyl residues were modified. From sequence analyses we concluded that the nature of the amino acid residues adjacent to the deiminated arginine were not modifiers of the reaction as arginyl residues in a variety of environments were deiminated. This deimination was reflected in a large increase in random structure, as measured by [θ] 200 . At 5°C, the [θ] 200 of the deiminated protein was ‐70 × 10 3 compared with ‐30 × 10 3 deg cm 2 /dmol for the native protein. When the temperature was increased to 70°C, the [θ] 200 was ‐44 × 10 3 for the deiminated protein and ‐20 × 10 7 deg cm 2 / dmol for the native C‐1. When plotted as a function of temperature, [θ] 200 decreased linearly from 5°C to 50°C for both proteins and did not change from 50°C to 70°C. PAD provides a mechanism for deimination of arginyl residues of myelin basic protein. The selective deimination of the six arginyl residues that are consistently found deiminated in C‐8 may be determined by the orientation of the protein in the membrane and/or the more complex lipid composition of myelin may affect the selectivity of the deimination.