Ribulose-peptide in human semen: II. Synthesis

In order to study the metabolism of a naturally occurring peptide containing D-ribulose in the semen, a pathway of D-ribulose synthesis from radioactively labeled glucose was analyzed. Semen obtained from ten healthy adults was used in this study. The seminal fluid of each person sampled was divided into two equal parts and each one was incubated with glucose-1-14C or glucose-6-14C at room temperature for 1 hr. The rate of incorporation into ribulose from glucose-6-14C was higher than that of glucose-1-14C. This suggests that the ribulose in semen might be converted from glucose through the pentose-phosphate cycle, and incorporated into the ribulose-peptide through an unknown pathway. Incorporation of the labelled 14C was also found in all of the amino acids which were detected in the acid hydrolysate of the ribulose-peptide.