P. Kalyankar et al. / Food Chemistry 136 (2013) 501–512
511
Fragments of
peptide (CMP f(105–169)) were also found in the
tion (Tables 1 and 2). Since chymosin was used during the initial
purification stages to obtain fractions enriched in -casein, it was
expected that -casein would be cleaved, but it was surprising to
observe peptide fragments corresponding to CMP in the enriched
-casein sample. CMP which is hydrophilic was not expected to
be present in the -casein fraction. However, it may have been
trapped in the -casein precipitate during the purification proce-
dure. The peptide fragments of -casein specifically released by
j
-casein specifically arising from caseino-macro-
Moreover, to our knowledge, this is the first demonstration of
the substrate specificity of GE on an actual food protein substrate,
i.e., a-casein.
a-casein prepara-
a
j
Acknowledgement
a
This work was funded under the National Development Plan
(2006-2010), through the Food Institutional Research Measure,
administered by the Irish Department of Agriculture and Food.
a
a
j
GE can be summarised as follows: f152–169 was observed in sam-
ples incubated for 30, 60, 120 and 240 min, f141–151 was observed
in samples incubated for 120 min and f120–126, f127–148, f131–
137 and f131–148 were observed in samples incubated for
240 min. During incubation at 37 °C only two CMP fragments,
i.e., f152–169 and f141–169, were observed in the samples incu-
bated for 15 min (Tables 1 and 2).
Overall, from the results obtained, it was observed that Glu-Pro
was not hydrolysed by GE, an observation also made by Breddam
and Meldal (1992) using synthetic peptides. It was also observed
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0
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0
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0
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P
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