PMID- 21282642
OWN - NLM
STAT- MEDLINE
DCOM- 20110414
LR  - 20211020
IS  - 1091-6490 (Electronic)
IS  - 0027-8424 (Print)
IS  - 0027-8424 (Linking)
VI  - 108
IP  - 7
DP  - 2011 Feb 15
TI  - Intramolecular proton shuttle supports not only catalytic but also noncatalytic 
      function of carbonic anhydrase II.
PG  - 3071-6
LID - 10.1073/pnas.1014293108 [doi]
AB  - Carbonic anhydrases (CAs) catalyze the reversible hydration of CO(2) to HCO(3)(-) 
      and H(+). The rate-limiting step in this reaction is the shuttle of protons 
      between the catalytic center of the enzyme and the bulk solution. In carbonic 
      anhydrase II (CAII), the fastest and most wide-spread isoform, this H(+) shuttle 
      is facilitated by the side chain of His64, whereas CA isoforms such as carbonic 
      anhydrase III (CAIII), which lack such a shuttle, have only low catalytic 
      activity in vitro. By using heterologous protein expression in Xenopus oocytes, 
      we tested the role of this intramolecular H(+) shuttle on CA activity in an 
      intact cell. The data revealed that CAIII, shown in vitro to have  approximately 1,000-fold 
      reduced activity as compared with CAII, displays significant catalytic activity 
      in the intact cell. Furthermore, we tested the hypothesis that the H(+) shuttle 
      in CAII itself can facilitate transport activity of the monocarboxylate 
      transporters 1 and 4 (MCT1/4) independent of catalytic activity. Our results show 
      that His64 is essential for the enhancement of lactate transport via MCT1/4, 
      because a mutation of this residue to alanine (CAII-H64A) abolishes the 
      CAII-induced increase in MCT1/4 activity. However, injection of 
      4-methylimidazole, which acts as an exogenous H(+) donor/acceptor, can restore 
      the ability of CAII-H64A to enhance transport activity of MCT1/4. These findings 
      support the hypothesis that the H(+) shuttle in CAII not only facilitates CAII 
      catalytic activity but also can enhance activity of acid-/base-transporting 
      proteins such as MCT1/4 in a direct, noncatalytic manner, possibly by acting as 
      an "H(+)-collecting antenna."
FAU - Becker, Holger M
AU  - Becker HM
AD  - AG Zoologie/Membrantransport and Abteilung fur Allgemeine Zoologie, FB Biologie, 
      University of Kaiserslautern, D-67653 Kaiserslautern, Germany. 
      h.becker@biologie.uni-kl.de
FAU - Klier, Michael
AU  - Klier M
FAU - Schuler, Christina
AU  - Schuler C
FAU - McKenna, Robert
AU  - McKenna R
FAU - Deitmer, Joachim W
AU  - Deitmer JW
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20110131
PL  - United States
TA  - Proc Natl Acad Sci U S A
JT  - Proceedings of the National Academy of Sciences of the United States of America
JID - 7505876
RN  - 0 (Bicarbonates)
RN  - 0 (Imidazoles)
RN  - 0 (Monocarboxylic Acid Transporters)
RN  - 0 (Protons)
RN  - 142M471B3J (Carbon Dioxide)
RN  - 33X04XA5AT (Lactic Acid)
RN  - EC 4.2.1.- (Carbonic Anhydrase II)
RN  - EC 4.2.1.- (Carbonic Anhydrase III)
RN  - Q64GF9FV4I (4-methylimidazole)
SB  - IM
MH  - Animals
MH  - Bicarbonates/metabolism
MH  - Biological Transport/physiology
MH  - Blotting, Western
MH  - Carbon Dioxide/metabolism
MH  - Carbonic Anhydrase II/chemistry/*metabolism
MH  - Carbonic Anhydrase III/chemistry/*metabolism
MH  - Catalysis
MH  - Humans
MH  - Hydrogen-Ion Concentration
MH  - Imidazoles
MH  - Lactic Acid/metabolism
MH  - *Models, Molecular
MH  - Monocarboxylic Acid Transporters/metabolism
MH  - Oocytes/metabolism
MH  - *Protons
MH  - Xenopus
PMC - PMC3041061
COIS- The authors declare no conflict of interest.
EDAT- 2011/02/02 06:00
MHDA- 2011/04/16 06:00
PMCR- 2011/08/15
CRDT- 2011/02/02 06:00
PHST- 2011/02/02 06:00 [entrez]
PHST- 2011/02/02 06:00 [pubmed]
PHST- 2011/04/16 06:00 [medline]
PHST- 2011/08/15 00:00 [pmc-release]
AID - 1014293108 [pii]
AID - 201014293 [pii]
AID - 10.1073/pnas.1014293108 [doi]
PST - ppublish
SO  - Proc Natl Acad Sci U S A. 2011 Feb 15;108(7):3071-6. doi: 
      10.1073/pnas.1014293108. Epub 2011 Jan 31.