Reference

Investigations of myelinogenesis in vitro: regulation of 5'-nucleotidase activity by thyroid hormone in cultures of dissociated cells from embryonic mouse brain

Investigations of myelinogenesis in vitro: regulation of 5'-nucleotidase activity by thyroid hormone in cultures of dissociated cells from embryonic mouse brain. Shanker, G.; Rao, G. S.; Pieringer, R. A. (Sch. Med., Temple Univ., Philadelphia, PA 19140, USA). J. Neurosci. Res., 11(3), 263-70 (English) 1984. CODEN: JNREDK. ISSN: 0360-4012. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) The developmental pattern of the myelin-assocd. 5'-nucleotidase [9027-73-0] and its regulation by L-3,3',5-triiodothyronine (T3) [6893-02-3] was demonstrated in a culture system of cells dissocd. from embryonic mouse brain. Hypothyroid calf serum contg. low levels of T3 (31 ng/100 mL) and thyroxine (T4) [51-48-9] (<1 mg/mL) was used in the culture medium in place of normal calf serum (T3, 103 ng/100 mL; T4, 5.7 mg/mL) to render the cultures responsive to exogenously added T3. By means of T3 supplementation, the lower levels of enzyme activity obsd. in the cultures grown in the presence of hypothyroid calf-serum contg. medium could be restored to a considerable extent, although not completely to normal values. Half-maximal stimulatory effect was obtained at 3.9 ′ 10-8M T3 concn. Among the various substrates tested, 5'-AMP [61-19-8], 5'-UMP [58-97-9], and 5'-CMP [63-37-6] were equally good, whereas 5'-GMP [85-32-5] yielded approx. half the activity.

Inactivation by acivicin of carbamoyl phosphate synthetase II of human colon carcinoma

Inactivation by acivicin of carbamoyl phosphate synthetase II of human colon carcinoma. Sebolt, Judith S.; Aoki, Takashi; Eble, John N.; Glover, John L.; Weber, George (Sch. Med., Indiana Univ., Indianapolis, IN 46223, USA). Biochem. Pharmacol., 34(1), 97-100 (English) 1985. CODEN: BCPCA6. ISSN: 0006-2952. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacology) Section cross-reference(s): 14 The effect of acivicin (I) [42228-92-2] (antitumor and antiglutamine drug) was detd. on the activity of the rate-limiting enzyme of de novo pyrimidine biosynthesis carbamoyl-phosphate synthetase II (glutamine-hydrolyzing) (EC 6.3.5.5) [37233-48-0] in human colon carcinoma. The synthetase II activity in human colon carcinoma was elevated 2- to 3-fold over values of the normal colon mucosa, and the substrate kinetic consts. were similar for the enzyme in normal and neoplastic colon. The KM for L-glutamine [56-85-9] was 17 mM (colon carcinoma) and 23 mM (normal mucosa), whereas the KM for ATP [56-65-5] was 2.1 and 1.7 mM in tumor and mucosa, resp. The synthetase II activity in colon carcinoma was inhibited to a similar extent by UMP [58-97-9], UDP [58-98-0] and UTP [63-39-8] (36-41%). The 3 uracil nucleotides were also equally effective in inhibiting the enzyme from normal mucosa (39-46%). Both enzymes were activated by PRPP [7540-64-9] (63 and 7%) in mucosa and carcinoma, resp. Acivicin in vitro selectively inactivated the glutamine-dependent synthetase II from human colon carcinoma, and it did not affect the ammonia-dependent activity. The acivicin inactivation const. was 100 mM, and the min. inactivation half-time was 0.7 min. Acivicin most likely exerts its effect against human colon synthetase II by acting as an active site directed affinity analog of L-glutamine.