Eleven amino acids were found in proteins from fresh
and traditional sun-dried pears (Table 2; Fig. 2b). In total,
they account for 4.23 mg per g of dry weight of the pulp in
the samples from fresh fruits in 2008 season and
3.37 mg g-1 in 2009. A value of 2.31 mg g-1 (dry weight)
for fresh pear (Pyrus communis L.) is reported in literature
[7], although from Beurre´ variety, which is lower than the
values for protein found for S. Bartolomeu fruits from both
harvests. In traditional sun-dried fruits, the amount of
protein amino acids was higher (18%) than in fresh in 2008
(5.00 mg g-1) and lower (6%) in 2009 (3.17 mg g-1).
For the fresh fruits, the most abundant protein amino
acids are Glx and Leu (20–19 mol%, each) and Asx
(17–13 mol%) (Fig. 2b). Also in relevant amount occur Ile
(10–7 mol%), Ala (8–7 mol%) and Val (7 mol%). Asx was
reported by Pilipenko et al. [7] as the predominant amino
acid in Pyrus communis L. fruits of Beurre´ variety
(35 mol%), showing that S. Bartolomeu pears present lower
relative amounts, although similar amounts are observed
when expressed in mg g-1. All amino acids found as constituents
of S. Bartolomeu pears have been also found in
Beurre´ variety. The exception is Hyp, not found in amounts
to be detected in S. Bartolomeu pears. Hyp is an amino acid
characteristic of extensins and arabinogalactan-rich glycoproteins.
Pyrus communis L. arabinogalactan-rich glycoproteins
from suspension cultures are composed mainly by
Glx (16 mol%) [28]. In Chinese species, reporting eight
pear varieties, Chen et al. [8] showed large variations in the
amino acid profile for the different pear varieties. Anyway,
Asn accounted for near 20% of total amino acids. In these
pears, Ser is the main constituent, although not always,
which is not the case of Pyrus communis L., where no Ser
was found.