several other organic solutes ( proline , 4-hydroxyproline , glycine , trimethylamine n-oxide , glycerol and myo-inositol ) that afford cryoprotection to phosphofructokinase , an effect enhanced by the addition of zinc , do not stabilize the enzyme during freeze-drying , even if zinc is present .
C0033382
proline
C0020388
4-hydroxyproline