Table 4.

PrtH and PepN activities of L. helveticus CRL 974 and CRL 1062 after growth in SCDM supplemented with different nitrogen sourcesa

MediumSp act of the following enzyme in the indicated strain:
PrtHbSp PepNc
CRL 974CRL 1062CRL 974CRL 1062
Basal SCDM129 ± 7192 ± 8468 ± 25122 ± 9
SCDM + 10-fold excess of amino acids132 ± 7195 ± 7460 ± 23112 ± 8
SCDM + 1% Casitone45 ± 317 ± 0.8433 ± 26140 ± 7
SCDM + 1% Casamino Acids115 ± 894 ± 4485 ± 32121 ± 9
SCDM + 1% β-casein72 ± 6114 ± 5402 ± 25132 ± 9
CDMWA + 1% Casitone46 ± 318 ± 0.9430 ± 26140 ± 8
MRS broth6 ± 0.36 ± 0.4405 ± 27138 ± 8
  • a Values are the means and standard deviations from three independent experiments.

  • b Specific activity is expressed as nanomoles minute−1 milligram of protein−1. LDH activity was less than 0.06% the total activity in each cell extract.

  • c Specific activity is expressed as micromoles minute−1 milligram of protein−1.