Unfortunately, discrepancies among recent reports have added to {HEAD ~ the general uncertainty} as to {TAIL ~ the true enzymatic function} for this family of proteins 
as to
Unfortunately , discrepancies among recent reports have added to { HEAD ~ the general uncertainty } as to { TAIL ~ the true enzymatic function } for this family of proteins
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH