Abstract
The activity of ATP sulfurylase, cysteine synthase, and cystathionine beta-lyase was measured in crude leaf extracts, bundle sheath strands, and mesophyll and bundle sheath chloroplasts to determine the location of sulfate assimilation of C(4) plant leaves. Almost all the ATP sulfurylase activity was located in the bundle sheath chloroplasts while cysteine synthase and cystathionine beta-lyase activity was located, in different proportions, in both chloroplast types.A new spectrophotometric assay for measuring ATP sulfurylase activity is also described.