Amino Acid Sequence in the N-Terminal Region of Taka-Amylase A

Abstract

Crystallization of Taka-amylase A (TAA) in 1952 in this laboratory (1,2) first opened a possibility to the systematic investigation of its chemical structure. It has already been reported that alanine is the only one N-terminal amino acid residue of the enzyme protein (3), and later work has led to a conclusion that the N-terminal region of the amylase molecule has the sequence, alanyl-glycyl-aspartic acid (4). The purpose of the present paper is to describe experiments undertaken to obtain more detailed information on the structure of the N-terminal part of the amylase protein. For this purpose a relatively large amount of TAA was dinitrophenylated and the resultant dinitrophenylated amylase (DNP-TAA) was subjected to partial hydrolysis. The DNP-peptides derived from the amino terminus were extracted from the hydrolysate and purified by counter-current distribution and other techniques. The amino acid compositions and sequences of the purified peptides were then determined by various analytical methods. It was thus concluded that the following sequence may be assigned to the N-terminal region of TAA ; alany 1-glycyl-aspartyl-glutamyl-seryl-alanyl-leucyl-threonine.