Abstract:
The impact of three different fabaceous host plants includ
ing cowpea (
Vigna
unguiculata
), chickpea (
Cicer arietinum
), and mung bean (
Vigna radiata
) seeds was
investigated using biochemical approaches on
possible changes of
gut proteolytic activity
of the cowpea weevil,
Callosobruchus maculatus
at
30±1 ̊C and 70±5% RH and a
photoperiod of 8:16 (L:D). Results revealed
that pH of 4
-
5 and 9 was optimal for the
activity of larval gut proteases using azocasein and hemoglobin as general substrates.
Different serine (
BApNA, SAAPFpNA,
PMSF, TLCK, and TPCK) a
nd cysteine (
Z
-
Arg
-
Arg
-
pNA, Z
-
Phe
-
Arg
-
pNA and DTT)
specific substrates inhibitors and activator were
used as a further proof of the proteolytic profile in the gut of
C. maculates
.
Although
combinations of serine and cysteine proteases were observed, the cy
steine proteases had
the highest rate on the studied hosts. The protease activity, especially cystein protease,
was the highest on cowpea, which was supported by hemoglobin (
0.156±0.045 U mg
-
1
)
, Z
-
Phe
-
Arg
-
pNA (2.85
U mg
-
1
)
substrates and DTT (90.00±0.10%)
as an activator. Due to the
importance and frequency of cysteine proteinases and their effects on biological and
physiological process, it would be better to design pest management programs based on
cysteine plant proteinase inhibitors as transgenic plants
.
Keywords:
C
hickpea
,
Cowpea, Cysteine proteinases, Digestive enzymes,
Mung bean.
