Influence of monoethanolamine on activity measurements of the isoenzymes of alkaline phosphatase.

Monethanolamine, a frequent impurity of diethanolamine, inhibits the activity of the isoenzymes of alkaline phosphatase to various extents. Isoenzymes from liver and bone, in particular, are strongly inhibited. Inhibition is stronger at lower (25 degrees C) than at higher temperatures (37 degrees C).

Suitability of commercial enzyme control sera for the quality control of activity determinations of L-aspartate aminotransferase and L-alanine aminotransferase in human serum.

Details of a systematic approach to suitability testing of commercial control sera are given for substrate optimized L-aspartate aminotransferase and L-alanine aminotransferase methods at 37 degrees C. Their acceptability for control purposes of standardized methods depends on: (1) the range of control values in relation to borderline values, (2) stability, (3) aspect, clarity, (4) NADH consumption in preincubation time, (5) blank activities, (6) kinetic data as half saturation constants and saturation curves, (7) influence of effectors, (8) isoenzyme pattern. These evaluation criteria are proposed for suitability testing.

Pyridoxal 5'-phosphate as an activator of the apoenzyme of alanine aminotransferase in human serum.

The relationship between reaction conditions and the stimulation of alanine aminotransferase by pyridoxal 5'-phosphate was investigated. Reaction conditions given for optimized alanine aminotransferase measurements are also optimal for measurements in the presence of pyridoxal 5'-phosphate taking into consideration the inhibitory effect of phosphate buffer. Addition of 150 mumol/1 pyridoxal 5'-phosphate to the reaction mixture guarantees a maximal stimulation after a pre-incubation period of 10 min.

Influence of auxiliary enzymes on the spectrophotometric measurement of alanine aminotransferase and aspartate aminotransferase activities.

We investigated the enzyme activity of the blank in the spectrophotometric determination of the aminotransferase activities and aspartate aminotransferase activity. 6 lactate dehydrogenase and 3 malate dehydrogenase preparations from different manufactures and from different organs showed additional and contaminating activity. The additional activity depends upon the 2-oxoglutarate concentration.

[A simple method for the synthesis of phosphatidylcholine with the fatty acid substituted in the 2-position].

The preparation of PC with the 14C-fatty acids palmitic, stearic, oleic and linoleic acid at OH-group in position 2 is described. The starting material is egg yolk lecithin. By the attack of snake venom phospholiphase lyso-PC is produced which is reacylated by the appropriate fatty acid anhydride.

Fatty acid pattern of lipids in normal and dystrophic human muscle.

The fatty acid distribution of the main lipid fractions: triglycerides (TG), phosphatidylcholine (PCh), phosphatidylethanolamine (PE), and sphingomyelin (Sph) of muscle from 6 patients with progressive muscular dystrophy (p.m.d.

[The influence of pyridoxal 5'-phosphate on the temperature relationships of aspartate aminotransferase isoenzymes].

The relationship between temperature and the behaviour of aspartate aminotransferase was investigated in the presence of pyridoxal 5'-phosphate. The addition in vitro of pyridoxal 5'-phosphate caused an increase in the activity and altered the thermal behaviour of aspartate aminotransferase. In choosing the temperature for the determination of enzymic activity, the concentration of the coenzyme must therefore also be considered.

[Phosphatidylcholine transfer between liposomes and mitochondria. Testing system for the study of specific phospholipid exchange].

A system consisting of liposomes and mitochondria for studying the exchange of specific phospholipids is described. The liposomes were prepared from phosphatidylcholine labelled with 14C-palmitic acid. The transfer of liposomes to the mitochondria is specifically stimulated 2- to 3fold by the pH 5.

[Influence of temperature on enzyme activity determination in serum : L-aspartate aminotransferase isoenzymes].

The influence of temperature on activity assays of the isoenzymes of L-aspartic aminotransferase in described. For this purpose, isolated human isoenzymes were added to inactivated serum. Half-saturation constants were determined at 17.