The word cleave is defined as to split or sever. The word after in the sentence BrAAP activity which cleaves after branched-chain amino acids means that splitting occurs following the branched-chain amino acids meet with bacteria.

The branched amino acids is used by the organism in protein where the polypeptide chain should be branched, other than that i think they're more or less just involved in transamination reaction and aminoacid-biosynthesis

It's not what "is" but what are ibcaa's

And it's "Instantized Branched Chain Amino Acids"

PROTEIN is made up of chain of amino acids.

PROTEIN is made up of chain of amino acids.