The increasing demand for interoperability in existing heterogeneous e-learning systems to support seamless accessibility, reusability and aggregation is an important research issue. Service Oriented Computing (SOC) enables interoperability between heterogeneous applications/systems over the Web. To adopt Web services technology towards the reusability and aggregation of e-learning services, the conceptual Web services architecture and its building blocks need to be augmented. In this paper, the authors propose a broker based e-learning Web service architecture which facilitates effective e-learning service publishing and discovery mechanisms. The paper suggests a scheme to extend the WSDL 2.0 to incorporate functional semantics of e-learning operations. The paper presents an e-learning service knowledge called Learning Operation Tree (LOT) for the quick discovery. The experimentation shows that, the proposed broker based architecture for e-learning Web services facilitates effective discovery with moderate performance in terms of recall and response.