in vitro aging at ph 7.4 , 37 degrees c causes natural sequence recombinant human growth hormone ( rhgh ) , methionyl rhgh , and human pituitary growth hormone to become substrates for bovine brain protein carboxyl methyltransferase , an enzyme that modifies the `` '' side chain '' '' alpha-carboxyl group present at atypical isoaspartyl linkages .
C0384570
rhgh
C0169964
human pituitary growth hormone