Epimerization of trans-4-hydroxy--proline to cis-4-hydroxy--proline during acid hydrolysis of collagen

Abstract

1. 1. trans-4-Hydroxy--proline is epimerized to cis-4-hydroxy--proline under the conditions generally used for the hydrolysis of proteins for analyses of amino acids.2. 2. The cis epimer elutes from a column of UR-30 resin on a Beckman amino acid analyzer at the same time as threonine and hence would be undetected.3. 3. About 8% of the trans-4-hydroxy--proline in collagen can be epimerized to cis-4-hydroxy--proline in the hydrolysis of collagen with 6 N HCl at 110[deg] for 72 hr.4. 4. A procedure is described whereby the primary amino acids in hydrolyzates are deaminated with nitrous acid and removed so that the amounts of trans-4-hydroxyproline, cis-4-hydroxyproline, and proline can be determined without changing the temperature of the column of UR-30 resin on the Beckman amino acid analyzer.