TABLE 3.

Maltose induction of MAL gene expression in strains carrying MAL61/HA61-90)a

MAL61-HA alleleMaltose fermentationbVmaxcMaltose transport activitycMaltase activityd
MAL61/HA+7.145.961,652
mal61/HA61-90)0.210.07320
ADH1-mal61/HA61-90)1.420.21463
Vector control0.080.0635
  • a Strain CMY1050 was transformed with a plasmid carrying the indicated MAL61/HA allele in vector pUN30 (12). Cells were grown in selective induced medium with 3% glycerol, 2% lactate, and 2% maltose to mid-log phase. Maltase activity and maltose transport activity were determined as described in Materials and Methods. Fermentation was determined as growth in rich medium (YP) + Maltose medium plus the production of gas within 7 days. Vmax was calculated by Lineweaver-Burk plotting of maltose transport activity over a range of substrate concentrations as described by Medintz et al. (23).

  • b +, maltose fermented; −, no maltose fermented.

  • c Expressed as nanomoles of maltose transported per milligram of cells per minute.

  • d Expressed as nanomoles of PNPG hydrolyzed per milligram of total protein per minute.