A sphingolipid pathway intermediate; natural isomer of dihydrosphingosine (sphinganine) that acts as a precursor of ceramide and sphingosine as well as a substrate of sphingosine kinases; increases in response to heat stress, indicating it is involved in heat stress adaptation in S. cerevisiae; levels increase significantly in response to certain mycotoxins, including fumonisins, as well as in some cancers; can block protein kinase C activation