TABLE 4.

Hydrolysis of 3HB oligomers by PhaZ1

OligomersaAbBcProduct spectra (HPLC)d
3HB oligomers
    R20<0.01No products of hydrolysis detectable
    R30.7340Monomer, dimer
    R41.11,430Dimer (traces: monomer and trimer)
    R51.31,970Dimer, trimer (traces: monomer)
    R61.81,220Dimer, trimer, (traces: tetramer)
    R83.1930Dimer, trimer (traces: monomer)
    R4S4+Monomer, dimer, trimer, pentamer
    S4R4++Monomer, dimer, pentamer
    R5S3++Dimer, trimer, tetramer (traces: monomer)
    S3R5++Dimer, trimer, tetramer (traces: monomer, pentamer)
    R6S2++Dimer, trimer (traces: monomer, tetramer)
    S2R6++Dimer, trimer, tetramer (traces: monomer,)
    R7S1++Dimer, trimer (traces: monomer, tetramer)
    S1R7++Dimer, trimer, tetramer (traces: monomer)
    [RS]4<0.01No products of hydrolysis detectable
    S4<0.01No products of hydrolysis detectable
    Bn-R4-t-butyl (protected)1,390ND
    Bn-S4-t-butyl (protected)<0.01ND
Cyclic oligomers (oligolides)
    oR1S3<0.01No products of hydrolysis detectable
    oR52,300Dimer, trimer
    oR61,840Dimer, trimer (traces: monomer, tetramer)
nPHB (trypsin activated)3,100Monomer, dimer, trimer
  • a R8, (R)-3HB octamer; R4S4, 3HB octamer consisting of [(R)-3HB]4 at the hydroxy terminus and [(S)-3HB]4 at the carboxy terminus; [RS]4, isotactic 3HB octamer consisting of four (R)-3HB-(S)-3HB building blocks; oR6, cyclic (R)-3HB hexamer; Bn, benzoyl.

  • b Equivalents of ester bonds cleaved within 24 h. After 2 h of continuous titration in a titristat, acid released was neutralized at 5-h intervals, accompanied by addition of fresh PhaZ1 in H2O.

  • c Specific activity corrected by spontaneous hydrolysis of the substrate. Values are in units per milligram; 1 U mg−1 = 1 μmol of acid min−1 mg of protein−1. Symbols represent qualitative results derived from end point titration: ++, >1,000 U/mg; +, >100 U/mg.

  • d ND, not determined.