Addition of pyridoxal-5'-phosphate to serum activates the
apo-enzymes and permits the measurement of total ASAT and
ALAT catalytic activity concentrations in serum. Provided the
saturation with P-5 '-P is complete, this eliminates bet\veen–
sample variations in the proportion of apo-enzyme. The avera–
ge increases relative to measurements of ASAT and ALAT with–
out activation are in the range 1.3 - 1.5 and 1.2 - 1.4, re–
spectively (l- lO a,b).
However, measurement of P-5'-p activated ASAT and ALAT chang–
es reference ranges previously established in the absence of
P-5'-P, since same apo-enzyme is almost always present in
healthy individuals. As ASAT and ALAT are activated to diffe-
rent
ALAT,
degrees, clinically useful ratios
and other enzymes are also changed.
between the ASAT,
In the majority of
cases clinical information is not significantly increased
through the use of P-5'-P campared with that obtained by me–
thods in \vhich this coenzyme is not added. This applies al so
to patients suffering from the relative deficiencies in B-vi–
tamins that may be encountered in Europe. However, the normal
or abnormally low levels of ASAT observed in some severely
ill patients in the absence of added P-5'-p may be converted
to abnormally raised values in assays with the added coenzyme
(4, 8, 9). Saturation of apo-ASAT and apo-ALAT in human sera
may be obtained in three ways, and different procedures have
been ehosen in various National recommendations (7- 16).
l. Incubation of sample in P-5'-P, 100 umol/L in reagent A.
start with 2-0xoglutarate (l, 2, 5-13)
Advantage: Complete activation in the majority of sera.
Can be automated.
Disadvantage: Prolangs incubation-activation time to 5 minu-
tes.
40
Klinisk kemi
i
Norden 2: supp/, 1990
