The exploration of pathways and alternative pathways that have a specific function is of interest in numerous chemical contexts. A framework for specifying and searching for pathways has previously been developed, but a focus on which of the many pathway solutions are realisable, or can be made realisable, is missing. Realisable here means that there actually exists some sequencing of the reactions of the pathway that will execute the pathway. We present a method for analysing the realisability of pathways based on the reachability question in Petri nets. For realisable pathways, our method also provides a certificate encoding an order of the reactions which realises the pathway. We present two extended notions of realisability of pathways, one of which is related to the concept of network catalysts. We exemplify our findings on the pentose phosphate pathway. Lastly, we discuss the relevance of our concepts for elucidating the choices often implicitly made when depicting pathways.

翻译：探索具有特定功能的路径及替代路径在众多化学背景下备受关注。此前已有框架用于指定和搜索路径，但未重点关注众多路径解决方案中哪些是可实现的或可使其成为可实现的。这里，“可实现”意指实际存在某种反应顺序，使得路径中的各反应能够依次执行。我们提出了一种基于Petri网可达性问题分析路径可实现性的方法。对于可实现路径，我们的方法还提供了一份证书，编码了实现该路径的反应顺序。我们提出了路径可实现性的两个扩展概念，其中一个与网络催化剂的概念相关。我们以磷酸戊糖途径为例验证了研究结果。最后，我们讨论了这些概念对于阐明在描述路径时通常隐含做出的选择的相关意义。