l. REACTION PRINCIPLEs
The reactions catalyzed by ALAT (I) and the indicator enzyme
(II) are as follow: (2 - 16)
L-alanine
+
2-oxoglutarate
pyruvate
+
+
NADH
+
H
L-Alanine Aminotransferase
,------
EC 2.6.1.2
Lactate dehydrogenase
,---------
EC
1.1.1.27
pyruvate
+
L-glutamate (I)
L-lactate
+
+
NAD
(II)
During the incubation-activation of sample with reagent A
(see below):
sample pyruvate
+
H
Lactate dehydrogenase
,-------
+
+
NAD
EC
1.1.1.27
L-lactate
+
NADH
+
(III)
The apoenzyme of ALAT is activated by addition of pyridoxal-
5'-phosphate before measurement. The sample pyruvate - NADH
+
+
H
reaction catalyzed by sample lactate dehydrogenase (LDH)
reaches completion during the
in~ubation
period. (l, 7- 16}.
The equilibrium of the indicator reaction (II) lies far to–
ward the productian of L-lactate. Therefore, the equilibrium
of the ALAT reaction (I) is not relevant, and the catalytic
active concentration of ALAT in the samples is determined by
the conversion rate of NADH (2).
58
Klinisk kemi
i
Norden 2: supp/, 1990
