الفهرس 
materialsOnly 14 pages are availabe for public view
 |  | from | 300 |  |  |
| | | from | 300 | | |
Abstract
In this study , two phospholipase A2 enzymes ( PLA )
were isolated from the Egyptian spitting cobra ( Naja
nigricollis ) crude venom ( ev ) , and their biochemical
biological and toxicological properties were studied
isolated enzymes were named ” PL-I ” and ” PL-II ” •
These
Part I of this work was isolation and purification
of PL-I and PL-II • Three chromatography steps were used.
First step chromatography was fractionation of ev by gel
filteration on Sephadex G-75 , which yeilded 4 fractions ,
Fl , F2 , F3 and F4 respectively • F2 showed highest PLA
activity Second step was isolation of PL-I and PL-II from
F2 by ion exchange chromatography using OAEA-Cellulose
PL-II was pure when tested by 50S-PAGE , whereas , PL-I was
not pure So PL-I was purified by a third step
chromatography using gel filteration on Sephadex G-IOO and
it was pure when tested with 50S-PAGE • Therefore , PL-I was
253
isolated in pure form by 3 chromatography steps while PL-II
by only 2 steps •
Part II of this study was biochemical
characterization of the isolated enzymes The molecular
weight of PL-I and PL-II were estimated by SDS-PAGE and were
found 13,500 and 14,000 respectively ~ of them were
1.36 X 10-4 M and 2.84 X 10-4 M and their Vmax were
19.23 ~g/hr and 18.52 ~g/hr respectively The optimum
temperature for PL-I activity was 650C and that of PL-II was
60
0
C • The optimum pH of both was 7.0 • Copper and calcium
ions enhanced activity of both enzymes whereas magnesium and
formaldehyde inhibited them •
Part III was in vitro study of some biological and
toxicological activities of the isolated enzymes comparing
with those of the CV • It was found that neither PL-I nor
PL-II had proteolytic activity while CV showed some
proteolytic activity • It was also found that ~L-I , PL-II
and CV had potent anticoagulant activities On testing
hemolytic activity , it was found that CV showed weak direct
254
hemolytic activity and both PL-I and PL-II han no direct
hemolytic activity but all of them showed very potent
indirect hemolytic activities •
Part IV of this study was in vivo study of the
biological and toxicological properties of the isolated
enzymes in comparison with the cv through I.M. injection of
experimental albino rats PL-I was found to had lethal
potancy similar to that of CV as LD~ of PL-I was 1.08 mgjkg
and the LD~o of CV was 15 mgjkg respectively • On the other
hand , PL-II was found to be non-lethal to rats up to 16
mgjkg ECG studies revealed that both PL-I and CV had
cardiotoxic effects with observing that arrhythmias were
predominant in CV induced cardiotoxicity , whereas , ischemia
was predominant in the cardiotoxicity induced by
Biochemical studies of some blood parameters ( TP
PL-I
, AP ,
ALT , AST , BUN and SC ) revealed that both PL-I and CV
affected liver and kidney functions with observing that PL-I
was more hepatotoxic and nephrotoxic than CV
Histopathological studies revealedc tha both PL-I and CV had
hepatotoxic , nephrotoxic and myotoxic effects with observing
that PL-I was more potent hepatotoxic , nephrotoxic and
myotoxic than CV •
255
from the results obtained in the present study , it
was concluded that the Egyptian Naja nigricollis venom
cotained two phospholipase A2 enzymes one of them ( PL-I )
was more potent and lethal than the other ( PL-II ) and at
least 2 steps of chromatography were essential for their
isolation in pure forms . It was also , concluded that PL-I
and PL-II had biochemical characters similar to that of PLA
enzymes isolated from othe snake venoms • In addition , it
was concluded that PL-I played a great role in the
anticoagulant , indirect hemolytic , cardiotoxic
hepatotoxic , nephrotoxic and myotoxic effects induced by
CV • Lastly , it was suggested that PL-I might be the only
nephrotoxic agent contained in CV •
It was recomended that , the Egyptian Naja
nigricollis venom should be more investigated and other
biologically active substances cotained in it should be
isolated and more characterized •