Team:Manchester/Enzyme

Uncertainty:

In synthetic biology two main classes of computational models are commonly used: constraint-based genome-scale models and differential-equation-based dynamic models. In our project, we employed the latter approach, because we are interested in the concentrations of compounds and their dynamic changes, which cannot be predicted using purely constraint-based models. We also wanted to identify the reactions and corresponding enzymes with the highest control over the fatty acid synthesis pathway; again, this is not possible with constraint-based models.

However, for a dynamic model one needs to know the enzyme kinetic parameters, and these are often unknown or very unreliable for enzymes of fatty acid biosynthesis. We wanted to account for the resulting uncertainty using a new “uncertainty modelling” approach, which can potentially serve as a principled approach to handling parameter uncertainty in the future.

Building models with incorporated acknowledgment of uncertainty will produce specified confidence intervals for all model predictions and thus could lead to robust design of engineered cellular machines of fatty acid synthesis and beyond.

Fatty Acid Biosynthesis

Fatty acid biosynthesis is a process that occurs in all living organisms. Glucose is converted into acetyl-coa through the citric acid cycle, which is fed into the fatty acid biosynthesis pathway. Here it combines with malonyl-CoA to first form a five carbon compound. The five carbon compound is then being converted into a four carbon compound via four successive steps, executed by the enzymes as indicated in Figure XXX . To this resulting C4 body, another malonyl-CoA is added to form a C7 body - which is converted the same manner as the previous C5 body. A number of unchanging enzymes act on the intermediates of this cyclic pathway to ultimately produce fatty acids. From the initial reaction to the end products the whole pathway numbers 43 reactions, about 60 metabolites and 267 parameters.

Steady State

The steady state of a metabolic system is the situation where the concentrations of the pathway intermediates remain constant, although there is metabolic flux through the system.