Table 3.

Effect of amino acid or glutamate analog additions on Gap1p activity

Amino acid or analog	Type of compound	Gap1p activity remaining 2 h after addition, %	Doubling time as a sole nitrogen source, h
No analog		100	2.9
l-glutamic acid	l-α-amino acid	3	3.2
l-cysteine	l-α-amino acid	2	>20
l-glutamine	l-α-amino acid	2	2.7
l-glycine	l-α-amino acid	6	>20
l-histidine	l-α-amino acid	1	>20
l-lysine	l-α-amino acid	18	>20
l-serine	l-α-amino acid	2	3.4
l-leucine	l-α-amino acid	1	5.7
l-alanine	l-α-amino acid	2	4.7
l-aspartic acid	l-α-amino acid	2	3.2
l-phenylalanine	l-α-amino acid	2	5.2
l-arginine	l-α-amino acid	8	2.9
l-threonine	l-α-amino acid	2	6.8
l-tyrosine	l-α-amino acid	2	5.6
l-tryptophan	l-α-amino acid	2	11.7
l-valine	l-α-amino acid	2	4.4
l-isoleucine	l-α-amino acid	2	6.1
l-methionine	l-α-amino acid	2	>20
l-asparagine	l-α-amino acid	2	2.8
l-citrulline	l-α-amino acid	7	6.9
l-ornithine	l-α-amino acid	11	13.4
l-proline	Imino acid	32	6.7
γ-Methylene-d,l-glutamic acid	l-α-amino acid	10	10.3
l-α-aminoadipic acid	l-α-amino acid	3	>20
l-methionine sulfoximine	l-α-amino acid	2	>20
l-methionine sulfoxide	l-α-amino acid	19	9.4
l-glutamic acid γ-ethyl ester	l-α-amino acid	7	7
β-Glutamic acid	β-Amino acid	24	>20
γ-Aminobutyric acid	γ-Amino acid	55	4.3
Allantoin	—	80	3.4
N-methylaspartic acid	N-methyl amino acid	97	>20
N-methylglutamic acid	N-methyl amino acid	89	>20
l-glutamic acid amide	Amide	92	>20

Gap1p activity was measured by [¹⁴C]citrulline uptake in a P_ADH1-GAP1-HA strain (CKY759) treated with the indicated amino acid or analog. All amino acids or analogs were dissolved in minimal ammonia medium, adjusted to pH 4, and added to 3 mM in minimal ammonia medium, except that those labeled with * were assayed at 0.75 mM and with ‡ was assayed at 0.5 mM. Assays were performed at least twice, in duplicate. Doubling times were measured for wild-type (CKY443) at 24°C in the presence of 6.8 mM amino acid or analog, the concentration routinely used for glutamate or glutamine minimal medium. All media were adjusted to pH 4. Those labeled with

^* were assayed for growth rate in the presence of 3 mM analog for solubility reasons and/or to allow comparison between the analogs shown in Figs. 4 and 5B. Also, the sample labeled with

^‡ was assayed for growth rate with 2 mM tyrosine for solubility reasons.

^†, These were at least partially toxic at ≥3 mM. However, cysteine is not toxic at the concentration shown, 0.75 mM.