Metabolism of Se-Selenite, Se-Selenate, Se-Selenomethionine and S-Sulfate by Rumen Microorganisms

Abstract

Studies were conducted to compare the metabolism of ⁷⁵Se-selenomethionine, ⁷⁵Se-selenite,⁷⁵Se-selenate and ³⁵S-sulfate by rumen microorganisms in vitro. There was a gradual incorporation of ³⁵sulfur activity into the TCA-insoluble fraction of the rumen fluid which could be inhibited by excess sulfate. The incorporation of ³⁵sulfur into methionine was confirmed by paper and ion exchange chromatography. There was a gradual incorporation of ⁷⁵Se-selenomethionine into the TCA-insoluble fraction of the rumen fluid which could be inhibited by excess methionine;Pronase released most of the activity from the TCA-insoluble fraction, approximately 60% of which was identified as ⁷⁵Se-selenomethionine by paper and ion exchange chromatography. Radioactivity added to the rumen fluid as ⁷⁵Se-selenite and ⁷⁵Se-selenate was rapidly incorporated into the TCA-insoluble fraction. However, most of the activity added as inorganic selenium was apparently loosely bound and could be removed by dialysis when reduced glutathione was in the dialysis bath; the binding of selenite was not enzyme dependent. The incorporation of inorganic selenium into the TCA-insoluble fraction was not inhibited by excess sulfate, and very little or none of the activity added to the rumen fluid as ⁷⁵Se-selenite or ⁷⁵Se-selenate was incorporated into ⁷⁵Se-selenomethionine. Copyright © 1968. American Society of Animal Science . Copyright 1968 by American Society of Animal Science