The deal value is about $7.2 billion including debt.
Under the terms Enable holders would receive about 0.86 Energy Transfer share for each of their units.
Energy Transfer shares closed on Tuesday at $6.96. Based on that close, 0.86 share would be valued at $5.99. Enable Midstream shares at last check were down 7.7% at $6.01.
Energy Transfer shares on Wednesday were trading off 1.4% at $6.86.
Additionally, each Enable Series A preferred share would be swapped for 0.027 Series G preferred unit of Energy Transfer.
And the transaction includes a $10 million cash payment to Enable's general partner.
Energy Transfer, the largest U.S. pipeline operator by revenue, says the transaction would help it deleverage.
The company expects that acquiring Enable will immediately add to free cash flow, boost its credit metrics, and add significant cash flow from fixed-fee contracts.
The deal would give Energy Transfer natural-gas gathering and processing assets in the Anadarko Basin in Oklahoma. And it would combine Enable Midstream's assets with Energy Transfer's current gas operations on the U.S. Gulf Coast.
Energy Transfer's purchase of Enable would be the company's second-largest deal by enterprise value, excluding the $28 billion deal that streamlined its operations in 2018, according to Bloomberg.
The current deal comes after a U.S. appeals court upheld a decision to deny a key permit to Energy Transfer's Dakota Access oil pipeline amid political pressure from indigenous tribes and environmentalists.
The Donald Trump administration opted to forgo any enforcement action against the pipeline. But the Joe Biden administration is seen as being more open to enforcing the court's decision, which could increase the risk that the nearly $4 billion, 1,172-mile pipeline, which brings shale oil from North Dakota to Texas, could shut down.