Novel time-temperature and ‘consume-within’ indicator based on gas-diffusion

The novel time-temperature indicator label comprises an ammonia sensitive indicator layer film pressed onto a second film, comprising an ammonia-generating, adhesive layer. When separated the blue-coloured indicator film reverts back to its original (ammonia free) yellow form at a controllable, temperature dependant rate. The labels are easily made and stored

Kinetic Analysis of the Non-Phosphorylated, \u3ci\u3eIn Vitro\u3c/i\u3e Phosphorylated, and Phosphorylation-Site-Mutant (Asp8) Forms of Intact Recombinant C\u3csub\u3e4\u3c/sub\u3e Phosphoenolpyruvate Carboxylase From Sorghum

Steady-state kinetic analyses were performed on the non-phosphorylated, in vitro phosphorylated and phosphorylation-site mutant (Ser8→Asp) forms of purified recombinant sorghum C4 phosphoenolpyruvate (P-pyruvate) carboxylase (EC 4.1.1.3 1) containing an intact N-terminus. Significant differences in certain kinetic parameters were observed between these three enzyme forms when activity was assayed at a suboptimal but near-physiological pH (7.3), but not at optimal pH (8.0). Most notably, at pH 7.3 the apparent Ki/ for the negative allosteric effector l-malate was 0.17 mM, 1.2 mM and 0.45 mM while the apparent Ka for the positive allosteric effector glucose 6-phosphate (Glc6P) at 1mM P-pyruvate was 1.3 mM, 0.28 mM and 0.45 mM for the dephosphorylated, phosphorylated and mutant forms of the enzyme, respectively. These and related kinetic analyses at pH 7.3 show that phosphorylation of C4 P-pyruvate carboxylase near its N-terminus has a relatively minor effect on V and Km (total P-pyruvate) but has a dramatic effect on the extent of activation by Glc6P, type of inhibition by l-malate and, most especially, Ka (Glc6P) and Kiv (l-malate). Thus, regulatory phosphorylation profoundly influences the interactive allosteric properties of this cytosolic C4-photosynthesis enzyme