In a review article I was reading recently to get some background information for an editing job, I encountered a sentence that I couldn’t decipher even after having read it several times. It serves as  a good example of how omitting words can lead readers down the garden path to a misinterpretation, or several possible misinterpretations. Here’s the sentence:

The cytosol contains enzymes that channel reducing equivalents from NADPH to small thiol-containing species and thiol/disulfide oxidoreductase enzymes (e.g., glutathione and thioredoxin) to reverse disulfide formation and other oxidative modifications of proteins.

One problem was that the placement of the parenthetical phrase “(e.g., glutathione and thioredoxin)” and the omission of the word “respectively” led me to misread the sentence as implying that glutathione is an example of an enzyme, which is not the case. The following revision solves that problem:

The cytosol contains enzymes that channel reducing equivalents from NADPH to small thiol-containing species (e.g., glutathione) and thiol/disulfide oxidoreductase enzymes (e.g., glutathione and thioredoxin) to reverse disulfide formation and other oxidative modifications of proteins.

What about the rest of the sentence? Did the author mean the following?

The cytosol contains enzymes that channel reducing equivalents [(1)] from NADPH to small thiol-containing species (e.g., glutathione) and [(2) from] thiol/disulfide oxidoreductase enzymes (e.g., thioredoxin) to reverse disulfide formation….

That can’t be right—reducing equivalents can’t be transferred to “reverse disulfide formation.” What about

The cytosol contains [(1)] enzymes that channel reducing equivalents from NADPH to small thiol-containing species (e.g., glutathione) and [contains (2)] thiol/disulfide oxidoreductase enzymes (e.g., thioredoxin) to reverse disulfide formation and other oxidative modifications of proteins.

There doesn’t seem to be anything counterfactual in this sentence; the cytosol does contain these two kinds of enzymes. However, after reading the reference cited at the end of the sentence, I settled on the following alternative interpretation, which, I think, is the correct one:

The cytosol contains enzymes that channel reducing equivalents from NADPH to small thiol-containing species (e.g., glutathione) and [from NADPH] to thiol/disulfide oxidoreductase enzymes (e.g., thioredoxin) to reverse disulfide formation and other oxidative modifications of proteins.

Note that besides separating the two parenthetical items in the original sentence, the only other change is the addition of the word “to” (or the phrase “from NADPH to”) to direct readers down the right path. One last tweak might be helpful though. Because some readers may wonder what the “to reverse disulfide formation” phrase modifies, the following revision might be the best option:

To reverse disulfide formation and other oxidative modifications of proteins, the The cytosol contains enzymes that channel reducing equivalents from NADPH to small thiol-containing species (e.g., glutathione) and to thiol/disulfide oxidoreductase enzymes (e.g, thioredoxin) to reverse disulfide formation and other oxidative modifications of proteins.

Readers familiar with the thioredoxin system might not have stumbled over the original sentence, but because it was in a review article, I contend that the suggested revision would have been clearer—assuming, of course, that I’ve interpreted the sentence correctly. Have I?

 

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