Biochemistry homework: Focus concept ripening fruit and the activity tin methyl- The link between the production of methanol in wild type and transgenic tomato esterase, the enzyme responsible for methanol production, is examined in fruit. Prerequisite Enzyme kinetics and inhibition. Background major source ofthis methanol is likely Methanol is produced by fruit during the ripening process. The to be from the enzyme p methylesterase which acts upon pectin methyl esters to de-esterify them and produce methanol and other pectic substances One might assume that the production of methanol is correlated with PME activity, but this has not been firmly established. In this case, the investigators at the Plant Science Department at Rutgers University developed a transgenic tomato which was deficient in PME activity. By comparing the behavior of the transgenic tomato with the wild type tomato, the production of methanol in the ripening tomato fruit may be better understood. Questions breaker (Br), turning (Tru) and red ripe (RR) tomatoes. They also determined the amount of PME protein present by using a Western blot assay, which uses a specific antibody to detect the PME protein. The results are shown in Figure 12.1. What is your interpretation ofthese results? Transgenio ING MG Be Figure 12.1: PME protein levels (A) and activ- ity (B) in wild-type and transgenic tomatoes. (Modified from Frenkel, et al. 1998.) Solution As given in A the protein level of PME is completely negligible in transgenic variety and present in wild type. In wild type variety the protein level in less in the IMG stage as compared to the subsequent stages this is because the expression of PME increases as the ripening of tomato increases. in fig. B : In the case of activity of the PME in the wild type variety increase is shown until it reaches the Tu stage and it starts decreasing in the fully ripening stage since the PME activity is not required to do the ripening. little activity in the transgenic variety is also shown because of the endogenous expression of PME because the PME is only altered not fully knockout.

1. Biochemistry homework: Focus concept ripening fruit and the activity tin methyl- The link
between the production of methanol in wild type and transgenic tomato esterase, the enzyme
responsible for methanol production, is examined in fruit. Prerequisite Enzyme kinetics and
inhibition. Background major source ofthis methanol is likely Methanol is produced by fruit
during the ripening process. The to be from the enzyme p methylesterase which acts upon pectin
methyl esters to de-esterify them and produce methanol and other pectic substances One might
assume that the production of methanol is correlated with PME activity, but this has not been
firmly established. In this case, the investigators at the Plant Science Department at Rutgers
University developed a transgenic tomato which was deficient in PME activity. By comparing
the behavior of the transgenic tomato with the wild type tomato, the production of methanol in
the ripening tomato fruit may be better understood. Questions breaker (Br), turning (Tru) and red
ripe (RR) tomatoes. They also determined the amount of PME protein present by using a
Western blot assay, which uses a specific antibody to detect the PME protein. The results are
shown in Figure 12.1. What is your interpretation ofthese results? Transgenio ING MG Be
Figure 12.1: PME protein levels (A) and activ- ity (B) in wild-type and transgenic tomatoes.
(Modified from Frenkel, et al. 1998.)
Solution
As given in A the protein level of PME is completely negligible in transgenic variety and present
in wild type. In wild type variety the protein level in less in the IMG stage as compared to the
subsequent stages this is because the expression of PME increases as the ripening of tomato
increases.
in fig. B : In the case of activity of the PME in the wild type variety increase is shown until it
reaches the Tu stage and it starts decreasing in the fully ripening stage since the PME activity is
not required to do the ripening.
little activity in the transgenic variety is also shown because of the endogenous expression of
PME because the PME is only altered not fully knockout