We describe a spectrophotometric kinetic assay for detecting creatine kinase MB isoenzyme activity in the 1 to 10 U/liter range. The MB isoenzyme was isolated [Clin. Chem. 20, 36 (1974)] and assayed (Rosalki method) with an Abbott ABA-100. Good reproducibility was demonstrated for MB isoenzyme activities near 1 U/liter (CV = 2.6%). Sera with normal or slightly increased total creatine kinase ac...

With p-nitrophenyl phosphate as the substrate, there reportedly is no organ-specific inhibition of alkaline phosphatase (EC 3.1.3.1) activity by L-phenylalanine. However, we found that at pH 10.0, with p-nitrophenyl phosphate as the substrate, L-phenylalanine obviously inhibits the alkaline phosphatase isoenzyme from human placenta, whereas there is little if any inhibition of the isoenzyme fro...

We observed an unexpectedly high incidence of the D-variant placenta! phenotype in Regan isoenzyme-positive sera of cancer patients-. Such D-variant-positive sera exhibit a high degree of inhibition by L-leucine, a phenomenon earlier associated with the Nagao isoenzyme. Unlike normal pla centae, a diffuse phenotype of heat-stable alkaline phosphatase is usually noted in cancer sera containing N...

The view is advanced that it is important to fix the stage of development corresponding to the pattern of expression of oncodevelopmental proteins in neoplastic transformation and neoplasia. From a map of development focused on events beginning with the zygote and ending with the establishment of fetus and placenta, it is possible to explain why certain develop mental gene products are restrict...

In serum obtained from 28 women before, during, and after normal labor and delivery, creatine kinase activity was seen to be distinctly elevated immediately after labor and 24 h later, but had returned to normal six weeks later. In most cases the increase was due to the MM isoenzyme and was attributed to skeletal-muscle damage associated with labor. In 15 cases, the BB isoenzyme was observed, a...

Creatine kinase isoenzyme MB catalytic activities in human serum, determined by ACA ion exchange chromatography and immunoinhibition, differ significantly, the correlation coefficient being 0.88. The reasons for this variation are interference of antibodies with the creatine kinase B subunit in the immunoinhibition assay, nonreproducible elution of creatine kinase isoenzyme MB from the ion exch...

A steady-state kinetic method has been revised for measuring lactate dehydrogenase isoenzyme activities, which relates the inhibition of heart-type isoenzyme activity to the overall isoenzyme composition of the enzyme subunits. The method depends on the pH-dependent formation of an inhibitory ternary complex by the heart-type isoenzyme with NAD+ and pyruvate (if the reaction is measured by NADH...

Pleurotus florida produces two extracellular laccase (L1 and L2) isoenzymes and the L1 isoenzyme is dominantly involved in the dye decoloration process. L1 isoenzyme was successfully purified to 6.4 fold with a yield of 36% and had a specific activity of 52.6 U mg of protein. The purified laccase was monomeric with an apparent molecular mass of ≈54 kDa. The optimum pH and temperature of the LI ...

We compared an alkaline phosphatase (EC 3.1.3.1) isoenzyme from a plasma sample of a patient with carcinoma of the lung, who was suspected of having the Regan-type isoenzyme, with placental serum alkaline phosphatase and with tissue preparations from placenta, liver, bone, and intestine. The placental and Regan phosphatases responded similarly to heat treatment and modification by various inhib...

1. Rat liver and heart major isoenzymes of NADP-isocitrate dehydrogenase have each been purified about 100-fold by a combination of ammonium sulphate fractionation and chromatography on ion-exchange cellulose and their properties compared. 2. The properties were similar in respect of pH, inhibition by Hg(2+) and Michaelis constants for isocitrate and NADP. 3. Some of the properties of the isoen...