Public procurement is a knowledge-based process. It involves, amongst others the knowledge of needs and trends, knowledge of concerned products or services, on their evolution in time and knowledge about actors able to offer them. The knowledge of political and legal context should be also considered as well as the environmental and social impact. Electronic procurement aims in reducing the amount of paper, but also in quicker and more knowledgeable processing of proposals and decision taking. We consider procurement activity as a part of a global organizational knowledge flow. This work goal is to analyze the whole process, identify the elements of knowledge necessary for successful purchase processing, to study the contribution of AI approaches and techniques to support the above elements. It is also to position e-procurement in the organizational knowledge flow.