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ASSAY OPTIMIZATION AND REGULATION OF UREASE ACTIVITY IN TWO MARINE DIATOMS
Author(s) -
Peers Graham S.,
Milligan Allen J.,
Harrison Paul J.
Publication year - 2000
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1046/j.1529-8817.2000.99037.x
Subject(s) - urease , thalassiosira pseudonana , biology , urea , nitrogen , ammonium , nitrogen assimilation , clone (java method) , thalassiosira weissflogii , botany , environmental chemistry , enzyme , biochemistry , ecology , chemistry , phytoplankton , nutrient , gene , organic chemistry
An in vitro urease enzyme assay was developed for the marine diatoms Thalassiosira pseudonana Hasle et Heimdal (clone 3H) and T. weissflogii (Grunow) Fryxell et Hasle (clone Actin). This assay involves the colorimetric measurement of ammonium following the hydrolysis of urea in crude cell homogenates and it is the first assay to account for the rate of nitrogen assimilation in both species grown on urea as the sole nitrogen source. Urease activity was found to be present regardless of nitrogen source, although activities showed distinctly different patterns depending on the species examined and form of nitrogen supplied. Under nitrogen‐replete conditions, urease activity in T. pseudonana was present constitutively when grown on NH 4 + and upregulated when grown on NO 3 − or urea. In nitrogen‐replete T. weissflogii , urease activity was present at high constitutive levels regardless of the nitrogen source and showed no upregulation. Nitrogen starvation did not upregulate activity in either species.