Studies on LM protein appearing in submandibular glands of isoproterenol-treated rats. II. Physicochemical properties.

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Abstract
Some physicochemical properties of the purified LM [large mobile] protein isolated from submandibular saliva of IPR[isoproterenol]-treated rats were studied. The MW of the LM protein was 12,000 and its isoelectric point was 4.75. The sugar content of the protein was 1.62% and the Ca content was 1.07 mol/mol protein. P and Mg were not detectable. Amino acid analysis revealed that the protein contained relatively large amounts of aspartic acid (asparagine) (14.8%), glutamic acid (glutamine) (14.8%) and serine (11.6%) and small amounts of proline (1.9%) and glycine (5.4%). A part of the amino acid sequence from the N-terminal was determined; the N-terminal was proline, followed by 5 hydrophobic amino acids. The LM protein isolated from submandibular glands of IPR-treated rats is evidently different from proline-rich proteins previously isolated by others from parotid glands of IPR-treated rats.