TABLE 1.

Effect of CD gene disruption on total CD activities and L-cysteine plus L-cystine production in E. coli

StrainGrowth (OD610)a after 15 h of cultivation in LB plus 30 mM l-cysteineCD activity (mU/mg of protein)b in the absence and presence of l-cysteineConcn of l-cysteine plus l-cystine after 72 h of cultivation in C1 + TS medium (mg/liter/OD562)c
No l-cysteine10 mM l-cysteine
JM39 (wild type)4.020.6 ± 0.127.6 ± 0.1590 ± 160
JM39ΔtnaA2.215.7 ± 0.114.1 ± 0.11,290 ± 70
JM39ΔmetC3.515.0 ± 0.127.6 ± 0.51,240 ± 100
JM39ΔcysK3.518.2 ± 0.529.9 ± 0.1NTd
JM39ΔcysM3.617.9 ± 0.527.8 ± 0.11,100 ± 70
JM39ΔmalY3.615.3 ± 0.127.1 ± 0.51,360 ± 90
JM39ΔtnaA ΔmetC ΔcysM ΔmalYNT9.1 ± 0.519.6 ± 0.11,080 ± 10
JM39ΔtnaA ΔmetC ΔcysK ΔcysM ΔmalYNT8.7 ± 0.511.5 ± 0.1NT
  • a The values are means from three independent experiments. The variations in the values were less than 10%.

  • b One unit of activity was defined as the amount of enzyme required to produce 1 μmol of sulfide per min from l-cysteine at 37°C. The values are means ± standard deviations from three independent experiments.

  • c The values are means ± standard deviations from three independent experiments.

  • d NT, not tested since cysK-disrupted cells showed l-cysteine auxotrophy.