Blood vessel injury was found to release intracellular pools of protein
D-aspartyl/L-isoaspartyl carboxyl methyltransferase (PIMT) into the extracellular
milieu, where it became trapped. Trapped PIMT was able to utilize radiolabeled
S-adenosyl-L-methionine (AdoMet) introduced into the circulation to methylate
blood vessel proteins containing altered aspartyl residues specifically at the site
of injury. In vitro studies more fully characterized this endogenous PIMT activity
in thoracic aorta and inferior vena cava. At least 50% of the PIMT activity
released during injury, was resistant to non-ionic detergent extraction,
suggesting that the enzyme activity can become trapped within or behind the
extracellular matrix (ECM). Analysis of inferior vena cava, found that 90% of the
altered aspartyl residues in blood vessels are inaccessible to methylation by
intracellular PIMT under physiological conditions. Subfractionation of inferior
vena cava on the basis of solubility found that at least 40% of the altered
aspartyl containing proteins in blood vessels are insoluble in non-ionic detergent containing buffers and are highly resistant to extraction by protein denaturants.
Analysis of peptides revealed that the majority of the altered aspartyl
groups in blood vessels are located extracellularly. Digestion of these
extracellular matrix proteins with cyanogen bromide (CNBr), followed by
methylation with (PIMT), found that about 60% of the altered aspartyl residues in
the ECM are solubilized by this treatment. The presence of hydroxyproline in
amino acid hydrosolates of this fraction and acidic pH gel electrophoresis of
methylated peptides, allowed the identification of collagen as the major PIMT
substrate in the CNBr-soluble material. CNBr peptides derived from both type I
and type III collagen were found to methylated. It is estimated that one
centimeter of blood vessel contains on the order of 5 x 10����� altered aspartyl
residues involving 1% to 5% of the total extracellular protein. / Graduation date: 1997
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34004 |
| Date | 12 August 1996 |
| Creators | Weber, Darin J. |
| Contributors | McFadden, Philip N. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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