In human benign prostatic hyperplastic (BPH) tissue homogenates 5alpha-reduction of testosterone was examined at neutral pH. As Lineweaver-Burk and Eadie-Scatchard plots of estimated initial velocities against a wide range of substrate concentrations of 2 nM to 3.2 microM were non-linear, the existence of two 5alpha-reductase isozymes in this tissue was surmised. Indeed, enzyme parameters at pH...

The liver is the most active organ engaged in S-adenosyl methionine metabolism . S-Adenosylmethionine synthetase isozymes (EC 2.5.1 .6) were studied in normal, fetal, and pathological livers including hepatoma to correlate their activities with developmental stages and pathophysiologi cal states of the liver. Three isozymes of S-adenosylme thionine synthetase, namely low, intermediate, and high...

A fundamental prediction of the hypothesis that critical events in tumour formation are rare is that the tumours develop by clonal expansion. This prediction has been tested by establishing the isozyme content of tumours induced in mosaic animals whose normal tissues contain two distinguishable isozyme activities. The observation that tumours contain activity associated with one or other of the...

Cytochrome P-450 isozyme 3a, isolated from hepatic microsomes of rabbits treated chronically with ethanol, was found to have a unique substrate specificity when compared with isozymes 2, 3b, 3c, and 4. Form 3a has unusually high activity in the p-hydroxylation of aniline and in the oxidation of alcohols to aldehydes. These properties are reflected in the increased activities of these substrates...

Two isozymes of 3-deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthase, denoted DS-Mn and DS-Co, were identified following DEAE-cellulose chromatography of crude extracts prepared from suspension-cultured cells of Nicotiana silvestris. The strikingly different properties of the isozymes allowed the development of assays for the selective detection of either isozyme in samples containing a ...

GLycolytic enzymes were studied from normal human retinas (both fetal and adult) and from retinoblastomas of eight patients and an established retinoblastoma cell line. No significant differences were found between the enzyme activities in the tissues investigated except for hexokinase and pyruvate kinase, which were significantly decreased in the tumor cells. In fetal retina, five different fo...

A new isozyme of cytochrome P-450, designated from 3a on the basis of its relative electrophoretic mobility, has been purified to homogeneity from liver microsomes of rabbits treated chronically with ethanol. This cytochrome has the highest activity of the known rabbit P-450 isozymes in the oxidation of ethanol to acetaldehyde. In view of the reports of others that the hepatotoxicity of acetami...

The rat prostate, a classical androgen-target tissue, contains both known isozymes of steroid 5alpha-reductase. i.e. type I and type II. So far, the role of the type I isozyme has been proposed as catabolic. The abundant expression of type I 5alpha-reductase in an androgen-target tissue is therefore puzzling. Assessment of the subcellular localization of 5alpha-reductase isozymes in rat prostat...

Two major ADH isozymes of mouse liver, basic ADH (Class I) and acidic ADH (Class III) were purified and the effects of various hydrophobic substances (t-butanol, butyramide, trifluoroethanol, trichloroacetic acid, stearic acid, oleamide, phenylalanine and norleucine) on their activities were investigated. All these hydrophobic substances activated acidic ADH with a range of from 15 to 560%, and...