Final answer:
Mercaptoethanol treatment of Calvin cycle enzymes might cause deactivation by breaking disulfide linkages and potentially leading to enzyme denaturation and loss of function.
Step-by-step explanation:
When Calvin cycle enzymes are treated with mercaptoethanol, a reagent known for breaking disulfide linkages, it might cause the deactivation of these enzymes. Since disulfide bonds often contribute to the tertiary or quaternary structure of proteins, breaking these linkages could lead to enzyme denaturation, which in turn might cause a loss of function. Unlike competitive or noncompetitive inhibition, where an inhibitor molecule impacts enzyme activity without breaking covalent bonds, mercaptoethanol would directly modify the structure of the enzymes by cleaving their disulfide bridges.
This action is a chemical modification of the enzyme rather than an inhibition by direct competition or allosteric effects with substrate molecules. Consequently, the enzymatic activity of the Calvin cycle enzymes is likely to be diminished, implying that option (5) 'It might deactivate them' is the most plausible effect of treating these enzymes with mercaptoethanol.