Table 2.

Ornithine decarboxylase activity in extracts of different strains

S. cerevisiae strain*	Chromosomal genotype	Plasmid	Ornithine decarboxylase activity nmol/hr/mg protein
BJ1991	SPE1SPE2	—	10
28-8D	spe2-4	—	80†
Y387	SPE1SPE2	pVT101U/SPE1	200–500
Y465	Δspe1∷LEU2	pVT101U/SPE1	2,000–6,000‡
	Δspe2∷LEU2

^*See Table 1. 

^† After growth in amine-deficient SD media for ≈66 hr. At this time, the cultures still showed logarithmic growth, but with a doubling time of about 18–20 hr. 

^‡ After growth in 5 × 10⁻⁵ M to 5 × 10⁻⁸ M spermidine. [Because yeast ornithine decarboxylase, purified to homogeneity from an E. coli strain with an overexpression plasmid, has an activity of 164,000 nmol/hr/mg protein (unpublished data), we estimate that approximately 2–4% of the soluble protein in the Y465 extract is ornithine decarboxylase.]