l. REACTION PRINCIPLEs
The reactions catalyzed by ASAT (I) and the indicator enzyme
(II) are as follow (l- l8):
L-aspartate
+
2-oxoglutarate
L-Aspartate aminotransferase
"'----
EC 2.6 . 1.1
Malate dehydrogenase
oxaloacetate
+
L-glutamate
I
+
Oxaloacetate
+
NADH
+
H
~---
__
--------_--------------~--~
L-ma late
+
II
EC 1.1.1.37
+
NAD
Du~ing
the incubation-activation of sample with reagent A
(see below):
sample pyruvate
+
+
NADH
+
H
Lactate dehydrogenase
,-----------
EC 1.1.1.27
L-lactate
+
+
NAD
III
The apoenzyme
5'-phosphate
+
of ASAT is activated by addition of pyridoxal–
before measurement (1). The sample pyruvate
+
NADH
+
H reaction catalyzed by sample lactate dehydrogenase
(LDH) reaches completion during the incubation period through
the inclusion of additional LDH in the incubation reagent (l,
7 - 16). The equilibrium of the indicator reaction (II) lies
far toward the productian of L-malate. Therefore, the equi–
librium of the ASAT reaction (I) is not relevant, and the
catalytic concentration of ASAT in the sample is determined
by the conversion rate of NADH (l).
42
Klinisk kemi
i
Norden 2: supp/, 1990
