Autor(es):
Barros, R. M. 
; Malcata, F. X.
Data: 2006
Identificador Persistente: http://hdl.handle.net/10400.14/6721
Origem: Veritati - Repositório Institucional da Universidade Católica Portuguesa
Assunto(s): whey protein; Hydrolysis; Aspartic protease
Descrição
Crude mixtures of aspartic proteases from flowers
of the plant Cynara cardunculus have been studied
frequently, as have activities of such enzymes (in pure
form) on caseins from bovine, ovine, and caprine
sources. This research study addressed pure bovine
whey protein as substrates; that is, α-lactalbumin (α-
LA) and β-lactoglobulin (α-LG), submitted to hydrolysis
by 1 of 2 aspartic proteases (cardosins A and B), previously
extracted and purified from C. cardunculus.
Samples collected, following incubation at 55°C and pH
5.2, were assayed by fast protein liquid chromatography,
reversed phase-high performance liquid chromatography,
and tricine-sodium dodecyl sulfate polyacrylamide
gel electrophoresis; the major peptides released
were then collected and sequenced by Edman degradation.
Cardosin B and, to a lesser degree, cardosin A
showed proteolytic activity toward α-LA, but the hydrolyzates
produced were characterized by distinct peptide
profiles. Cardosin B possesses a broad specificity, and
produces several hydrophobic peptides (at least 5, with
molecular mass in the range 2 to 8 kDa) in the early
stages, which eventually become more hydrophilic
(with molecular mass below 2 kDa) at later stages of
hydrolysis. Cardosin A was found to cleave α-LA at the
peptide bonds Phe28-Arg29, Gly54-Tyr55, Ala59-Ile60,
Leu71-Phe72, and Leu105-Thr106, whereas cardosin B
cleaved Ala19-Glu20, Phe28-Arg29, Glu30-Leu31,
Tyr37-Gly38, Trp45-Val46, Phe50-His51, Ala59-Ile60,
Ser66-Thr67, Leu71-Phe72, Phe72-Gln73, Gln73-Ile74,
Ile78-Trp79, Leu115-Asp116, and Leu124-Ala125. Conversely,
cardosins A and B are apparently not active
on β-LG.
