Analysis of human pictuitary growth hormone and its charge varriants by fast‐atom bombardment mass spectrometry

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Abstract
There is evidence that even highly purified preparations of human growth hormone are not homogenous, but contain charge as well as size variants. The charge heterogeneity was suggested to be due to deamidation of the native hormone. To verify this we have applied peptide mapping followed by fast‐atom bombardment mass spectrometry (FAB‐MS), in order to identify fragments containing the altered amino acids. Growth hormone was purfied from human pituitaries and the differently charged forms were separated by column electrophoresis in agarose suspension. The isolated components were treated with trypsin and analysed directly by FAB‐MS without prior separation by reversed‐phase high‐performance liquid chromatography (RP‐HPCL). Using this technique, approximately 80% of the normone structure was recovered and two deamidation sites were found in the fragment T15 (FDTNSHNDDALLK). The results clearly elucidated the potential use of FAB‐MS for the fast secreening of other variants of the growth hormone which are known to exist.