Serum apo-aminotransferases reassociate equally well with pyridoxal 5'-phosphate in water or buffer.

(-300 words text) summarize findings that are of interest to a relatively limited audience. Readersdesiringfuller details may obtain them by writing directly to the author(s) at the address given. Briefs dealing with procedure or instrumentation intercompari-sons,evaluations, or improvements(including kit applications) shouldbe sent to As is well known. the coenzyme pyridoxal 5'-phosphate (PU') enhances the activity of serum aspartate ansinotrans-ferase (Asr, EC 2.6.1.1) and alanine aminotransferase (ALT, EC 2.6.1.2) (1, 2). It can be added to the total reagent mixture (less 2-oxoglutarate) for quantifying these enzymes, as has been described in many recommendations, or it can be added to the serum, 10-mm pro-incubation being necessary in either case. The reaction can then be started by adding either the substrate or the serum including the coenzyme. When serum is pro-incubated with P12, the added PLP must be dissolved in Tha buffer, for it can bind to the lysine in serum albumin when P12 is dissolved in water (3, 4). We investigated any difference between the activity concentration measured for serum AST and ALT, after dissolving P12(1.12 mmol/L final concentration) in water or Tris buffer (pH 7.8; 50 mmolfL) before starting the reaction with serum. After a 10-mm pro-incubation, the reaction was started and results were measured at 30#{176}C in a centrifugal analyzer. We also measured activity concentrations according to the recommendations of the IFCC (5, 6), starting the reaction with 2-oxoglutarate. Volume fractions of sample were the same in both experiments: 0.083. In the statistical analysis we used Student's t-test for paired observations. It is obvious from the following tabulation that PLP enhances the measured activity concentration: