The State authority is hereby declared to be performing a public function in behalf of the State and to be a public instrumentality of the State. Also, for purposes of the Illinois Securities Law of 1953, compiled as Sections 137.1 through 137.17 of Chapter 121 1/2 Ill. Rev. Stats. 1969, and any amendment thereto and substitution therefor, bonds issued by any such authority shall be deemed to be securities issued by a public instrumentality or a political subdivision of the State of Illinois. To the extent permitted by the Constitution the property acquired by the State authority pursuant to this Act is exempt from taxation except that during any period that such property is leased or sold or is subject to an agreement to be leased or sold by such authority, taxes shall be payable to the same extent as if it were owned by such lessee or purchaser, or prospective lessee or purchaser, and such taxes shall be paid by such person.