Regulation of Carbonic Anhydrase Expression by Zinc, Cobalt, and Carbon Dioxide in the Marine Diatom Thalassiosira weissflogii  

Abstract

TWCA1 is the major Zn-requiring isoform of carbonic anhydrase (CA) in the marine diatom Thalassiosira weissflogii. We have examined the roles that trace metals and CO 2 play in the regulation of TWCA1 expression over ranges of concentrations that bracket those encountered in the marine environment. Both steady-state levels of TWCA1 and the kinetics of induction were measured by western analysis. TWCA1 levels correlated well with cellular CA activity levels. TWCA1 was induced at a low CO 2 concentration but the level of induction, as determined by western analysis, was dependent on the availability of Zn. Co effectively substituted for Zn in regulating TWCA1 expression and promoting TWCA1 activity. Upon shift from low to high CO 2 , the concentration of TWCA1 decreased. The expression of TWCA1 is diel cycle regulated, and cellular TWCA1 decreased during the dark phase. These results provide the basis for studying the expression of CA in field populations and, taken together with previous radiolabeling studies, provide strong evidence of in vivo metal substitution of Co for Zn in a CA. Our data also support the conclusion that TWCA1 plays a central role in carbon acquisition in T. weissflogii.

A seasonal study of dissolved cobalt in the Ross Sea, Antarctica: micronutrient behavior, absence of scavenging, and relationships with Zn, Cd, and P

“…1a and b). We suggest two interrelated reasons for this: first, the high ratio of dissolved Zn:Co in the Ross Sea described above likely results in high Zn uptake and resultant minor Co uptake and use in the cambialistic enzymes within the phytoplankton community, as observed in laboratory culture studies (Sunda and Huntsman, 1995;Lane and Morel, 2000). Second, as mentioned above, these low dissolved Co:PO 3− 4 ratios are less than that required for optimal phytoplankton growth without supplementation with Zn (Sunda and Huntsman, 1995).…”

“…Physiological evidence of this Co-Zn substitution has been demonstrated in the Ross Sea phytoplankter Phaeocystis antarctica . In addition, low pCO 2 is known to cause several fold increases in the Cd:P ratio of particulate material in field experiments off the coast of California, likely due to upregulation of carbonic anhydrase enzymes (Lane and Morel, 2000;Cullen and Sherrell, 2005). Co geochemistry is also tied to that of Mn, where it has been shown that Co can be co-oxidized by manganeseoxidizing bacteria, and this is likely a critical pathway for the scavenging removal of Co from seawater (Tebo et al, 1984;Moffett and Ho, 1996).…”

“…While, as mentioned above, Co is required for the biomolecule B 12 , it is also one of three elements (with Zn and Cd) that are capable of substituting in the active site of two important marine carbonic anhydrase metalloenzymes (the Zn/Co DCA1 and the Cd/Zn CdCA1), while maintaining enzymatic activity (Roberts et al, 1997;Lane et al, 2005).…”

Effect of iron limitation on the cadmium to phosphorus ratio of natural phytoplankton assemblages from the Southern Ocean

“…The surface water geochemistry of Zn and Cd are closely linked through the physiological requirements of the phytoplankton. The fact that Cd can substitute for or supplement Zn in the enzyme carbonic anhydrase (CA) (Price and Morel 1990;Morel et al 1994;Cullen et al 1999;Lane and Morel 2000b) or as part of a Cd-specific CA (Lane and Morel 2000a) has been cited as the reason for the biological uptake of Cd in surface waters. Indeed, Zn-amended phytoplankton assemblages from Monterey Bay had lower Cd : P ratios than controls without added Zn (Cullen et al 1999).…”

Inhibition of Carbonic Anhydrase II by Thioxolone: A Mechanistic and Structural Study

“…CAs are found in most eukaryotic and many microbial organisms (9,10). There are currently five known CA structural families, the structurally characterized R-, -, and γ-classes and the more recently discovered δ-and -classes (2,7,8,(11)(12)(13)(14)(15). The zinc-dependent R-class CAs are the most clinically relevant family, with at least 14 known isoforms expressed in mammalian tissues (11,(16)(17)(18).…”