Linked Life Data

7662592

Source:http://linkedlifedata.com/resource/pubmed/id/7662592

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3-4
pubmed:dateCreated
1995-10-10
pubmed:abstractText
Reevaluating the assay for rat steroid 5 alpha-reductase isozymes in prostate and epididymis homogenates we encountered an extreme pH-dependency of the type II isozyme. The time-course of the metabolism of testosterone (T) to 17 beta-hydroxy-5 alpha-androstan-3-one (DHT) at acidic pH shows an initial burst when the homogenate is not brought to pH before the start of the incubation. Therefore, the rat type II 5 alpha-reductase isozyme does not follow Michaelian law under these conditions making a single time point measurement invalid. Assessing the pH-optimum of 5 alpha-reduction in both rat prostate and epididymis homogenates we found a strong substrate dependency: at high substrate concentrations a pH-optimum for the type II isozyme of pH 5.0 was found, whereas at lower concentrations pH 5.5 is optimal. Establishing Vmax (maximum velocities) and Km (affinity constants) for the 5 alpha-reduction of T at pH 4.5-8.0, the efficiency optimum Vmax/Km appeared to be pH 5.5 in both prostate and epididymis homogenates. Specifically at acidic pH these kinetic characteristics of the type II isozyme vary many-fold. Discrepancies in literature concerning 5 alpha-reductase characteristics can, at least in part, be attributed to the choice of optimal pH, or to pH shifts during the assay.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0960-0760
pubmed:author
pubmed:issnType
Print
pubmed:volume
54
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
185-92
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Rat steroid 5 alpha-reductase kinetic characteristics: extreme pH-dependency of the type II isozyme in prostate and epididymis homogenates.
pubmed:affiliation
Department of Medicine, University of Hospital, Nijmegen, The Netherlands.
pubmed:publicationType
Journal Article