PURIFICATION, PROPERTIES AND N-TERMINAL AMINO-ACID-SEQUENCE OF A WHEAT GLUTEN ASPARTIC PROTEINASE

An aspartic proteinase (EC 3.4.23) was purified 31 300-fold with 6% re covery from wheat gluten by ammonium sulphate precipitation, affinity- chromatography on pepstatin A-agarose and gel permeation chromatograph y. The enzyme has no amino- or carboxypeptidase activity and is a hete rodimer with subunits of apparent molecular mass. c. 11 and 29 kDa. It has an iso-electric point of c. 4.55. The enzyme is maximally active against haemoglobin at pH 2.5 and between 45-50 degrees C and is compl etely inhibited by pepstatin A. The sequence of the first 20 N-termina l amino acids of the 11 and 29 kDa subunits have 90% and 95% identity, respectively, with the N-terminal amino acid sequences of the 11 and 29 kDa subunits of barley aspartic proteinase. (C) 1998 Academic Press .