Glucose 6-phosphate dehydrogenase from human erythrocytes: identification of N-acetyl-alanine at the N-terminus of the mature protein.

Glucose 6-phosphate dehydrogenase from human erythrocytes has a blocked amino-terminus and no information could be obtained by direct sequencing of the intact protein. The peptide corresponding to the amino-terminal region was isolated from a tryptic digest of the whole protein and identified on the basis of its amino acid composition and of the failure to obtain Edman degradation. Determination of peptide mass by fast atom bombardment mass spectrometry allowed identification of the blocked amino-terminal residue as N-acetyl-alanine.