Cell-associated proteolytic enzymes from marine phytoplankton

Journal Article · Thu Aug 01 04:00:00 EDT 1996 · Journal of Phycology

DOI:https://doi.org/10.1111/j.0022-3646.1996.00566.x· OSTI ID:468355

Berges, J A; Falkowski, P G ^[1]

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1. Brookhaven National Lab., Upton, NY (United States)

Despite their central importance in cell metabolism, little is known about proteases in marine phytoplankton. Caseinolytic and leucine aminopeptidase (LAP) activities was surveyed in log-phase cultures of the chlorophyte Dunaliella tertiolecta Butcher, the diatom Thalassiosira weissflogii Fryxell et Hasle, the chrysophyte Isochrysis galbana Parke, the coccolithophorid Emiliania huxleyi Hay et Mohler, and the cyanobacterium Synechococcus sp. LAP activity was very low at pH < 6 and peaked between pH 7.5 and 8.5 in all species, whereas caseinolytic activity in most species showed only minor peaks in the pH 4-5 range and broad maxima above pH 8. Acidic vacuolar proteases apparently represented only a small fraction of total protease activity. Attempts to classify protease using selective inhibitors were inconclusive. Caserinolytic activities were remarkably stable. Casein zymograms were used to identify >200-and <20-kDa proteases in homogenates of log-phase T. weissflogii; only the smaller protease was found in D. tertiolecta. Antibodies in the ATPase subunit (C) of the conserved, chloroplastic Clp protease from Pisum cross-reacted with proteins in Synechococcus, D. tertiolecta, and I. galbana, but no cross-reactions were found for any species with antibodies against the ClpP subunit from either E. coli or Nicotiana. Our results show that phytoplankton contain a diverse complement of proteases with novel characteristics. 46 refs., 6 figs., 1 tab.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 468355
• Journal Information: Journal of Phycology, Journal Name: Journal of Phycology Journal Issue: 4 Vol. 32; ISSN JPYLAJ; ISSN 0022-3646
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
BIOCHEMISTRY
ENZYMES
PHYTOPLANKTON
PROTEOLYSIS