It is quoted in wikipedia that:

Following the EC number classification, they belong to the group of ligases , with lyases catalysing the reverse reaction.

And we all know that enzymes are biocatalysts which catalyses reaction in both forward and backward directions.

So my question is that how can the reaction in one direction catalysed by one enzyme and in reverse direction catalysed by other enzyme? If we assume that they are telling that one direction synthase acts as ligase and in other direction it acts as lyase then how can lyases have more than one substrate for reaction? Because products(more than one) of ligase acts substrate for reverse reaction.(taking for example a ligase, glutamine synthetase as synthase)

It is also quoted from wikipedia

Lyases differ from other enzymes in that they require only one substrate for the reaction in one direction, but two substrates for the reverse reaction.