Prochlorococcus marinus strain PCC 9511, a picoplanktonic cyanobacterium, synthesizes the smallest urease The GenBank accession number for the sequence determined in this work is AF242489.

Abstract

The urease from the picoplanktonic oceanic Prochlorococcus marinus sp. strain PCC 9511 was purified 900-fold to a specific activity of 94.6 µmol urea min N1 (mg protein) N1 by heat treatment and liquid chromatography methods. The enzyme, with a molecular mass of 168 kDa as determined by gel filtration, is the smallest urease known to date. Three different subunits with apparent molecular masses of 11 kDa (γ or UreA ; predicted molecular mass 11 kDa), 13 kDa (β or UreB ; predicted molecular mass 12 kDa) and 63 kDa (α or UreC ; predicted molecular mass 62 kDa) were detected in the native enzyme, suggesting a quaternary structure of (αβγ) 2 . The K m of the purified enzyme was determined as being 023 mM urea. The urease activity was inhibited by HgCl 2 , acetohydroxamic acid and EDTA but neither by boric acid nor by L-methionine-DL-sulfoximine. Degenerate primers were designed to amplify a conserved region of the ureC gene. The amplification product was then used as a probe to clone a 57 kbp fragment of the P. marinus sp. strain PCC 9511 genome. The nucleotide sequence of this DNA fragment revealed two divergently orientated gene clusters, ureDABC and ureEFG, encoding the urease subunits, UreA, UreB and UreC, and the urease accessory molecules UreD, UreE, UreF and UreG. A putative NtcA-binding site was found upstream from ureEFG, indicating that this gene cluster might be under nitrogen control.

Streamlined Regulation and Gene Loss as Adaptive Mechanisms in Prochlorococcus for Optimized Nitrogen Utilization in Oligotrophic Environments

“…This hypothesis is also supported by the similarly simple behavior of other nitrogen-related regulatory proteins (P II [56] or NtcA [33]) (Fig. 2C and D), enzymes (urease [55]), or transporters (the ammonium transporter encoded by amt1 [33]) (Fig. 2D).…”

“…The measured urease activities were fairly constant irrespective of the nitrogen source supplied to Prochlorococcus strain PCC 9511. This apparent lack of regulation, similar to that observed for GS, led to hypothesize that NtcA was not involved in the control of urease biosynthesis in Prochlorococcus, in spite of the presence of putative NtcA binding sites located next to the ure genes (encoding the urease structural and accessory molecules) (55). These genes are organized in two overlapping, opposite clusters in Prochlorococcus strain PCC 9511 (55) and Synechococcus strain WH 7805 (7), in contrast to the case for most freshwater cyanobacteria, where these genes are scattered throughout the genome (55).…”

Identification of PamA as a PII-binding Membrane Protein Important in Nitrogen-related and Sugar-catabolic Gene Expression in Synechocystis sp. PCC 6803

“…These genes, except for ureG, are known to be controlled by NtcA (36). The ureG gene, which encodes a urease accessory protein, was shown to be regulated by NtcA in Prochlorococcus marinus PCC 9511 (37) and, therefore, could also be regulated by NtcA in Synechocystis sp. PCC 6803.…”

Urease activity in cultures and field populations of the toxic dinoflagellate Alexandrium

“…Growth on urea, urea uptake, or urease activity have been demonstrated for many different phytoplankton species (Carpenter et al 1972;Antia et al 1991;Collier et al 1999;Palinska et al 2000;Berg et al 2002), although not for many dinoflagellates. Urea is assimilated by hydrolysis to ammonia via either the enzyme urease or adenosine triphosphate (ATP) urea amidolyase in marine phytoplankton (Antia et al 1991).…”