Missing direction information in reactions.dat file

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No, if no reaction direction is listed, it is not safe to make any assumption about it. In general, reactions are defined in a direction (i.e. the left and right slots) according to EC conventions, which may have little bearing on the physiological direction. When we specify a reaction direction, it is either because our curators have specifically curated that direction based on the literature or on chemical knowledge, or because the software can infer a direction based on the direction it goes within some pathway or when catalyzed by some enzyme. If we don't have the information to make an inference, and a curator has not specifically examined the reaction, we don't assign one. This doesn't necessarily mean the direction is unknown -- some of the reactions imported from the EC have comments that make the direction clear, but that info is not in a form that is interpretable by our software.