Source of H+ ions and Lactate

[Maria87]

Hi All,

I was just wondering if you know of any other source of hydrogen ions and lactate production in a cell APART from glycolysis?
ie, is it produced by normal cellular processes?
According to me, H+ and lactate are produced under hypoxic conditions. Glucose is broken down into lactic acid with then dissociates into lactate and H+.

If you know please let us know,
Many thanks

[Airtones]

H+ ions are made from CO2 and H2O during ordinary respiration.

(CO2) + (H2O) <--> (H+) + (HCO3)

This happens to about 30% of the CO2 that comes into the body. The other 70% is made into carbonic acid like:

(CO2) + (H2O) <--> (H2CO3)

It is possible with carbonic anhydrase (I know its present in erythrocytes at least) to then dissociate a hydrogen ion from H2CO3:

(H2CO3) --> (H+) + (HCO3)

This actually happens anyway but its negligably slow without the enzyme. The enzyme carbonic anhydrase is actually a family of enzymes and they're quite interesting as they use a zinc ion as a prosthetic group rather like haemoglobin uses Fe2+. Hence the need for dietry zinc!

[Maria87]

ya I totally agree with you about the Carbonic anhydrase.

Q: Is lactate produced by the cell by any means APART from glycolysis? or is lactate the endproduct of any chemical reaction taking place in the cell(which doesn't need O2) apart from glycolysis?

PS: I know that cells make use of lactate as a fuel/ for migration/signalling/,... but I know little about the source of lactate in the cell apart from production by glycolysis. E.g. If a cell fully oxidises glucose into CO2 then will there be zero intracellular lactate? It would be really appreciated if you can shed some light into this.

Thanks