Phosphoenolpyruvate carboxylase activity, fixation of14C in amino acids and nitrogen transport in stem nodules ofSesbania rostrata

1993 ◽  
Vol 35 (2) ◽  
Author(s):  
S. Sadasivam ◽  
P. M. Lakshmi ◽  
S. Kannaiyan
Keyword(s):  
Amino Acids ◽  
Phosphoenolpyruvate Carboxylase ◽  
Nitrogen Transport ◽  
Carboxylase Activity

scholarly journals A conserved C-terminal peptide of sorghum phosphoenolpyruvate carboxylase promotes its proteolysis, which is prevented by Glc-6P or the phosphorylation state of the enzyme

Planta ◽  
2021 ◽  
Vol 254 (3) ◽  
Author(s):  
Jacinto Gandullo ◽  
Rosario Álvarez ◽  
Ana-Belén Feria ◽  
José-Antonio Monreal ◽  
Isabel Díaz ◽  
...  
Keyword(s):  
Amino Acids ◽  
Phosphoenolpyruvate Carboxylase ◽  
Synthetic Peptide ◽  
Phosphorylation State ◽  
Allosteric Effector ◽  
Cathepsin Proteases ◽  
Photosynthesis Pathway

Abstract Main conclusion A synthetic peptide from the C-terminal end of C4-phosphoenolpyruvate carboxylase is implicated in the proteolysis of the enzyme, and Glc-6P or phosphorylation of the enzyme modulate this effect. Abstract Phosphoenolpyruvate carboxylase (PEPC) is a cytosolic, homotetrameric enzyme that performs a variety of functions in plants. Among them, it is primarily responsible for CO2 fixation in the C4 photosynthesis pathway (C4-PEPC). Here we show that proteolysis of C4-PEPC by cathepsin proteases present in a semi-purified PEPC fraction was enhanced by the presence of a synthetic peptide containing the last 19 amino acids from the C-terminal end of the PEPC subunit (pC19). Threonine (Thr)944 and Thr948 in the peptide are important requirements for the pC19 effect. C4-PEPC proteolysis in the presence of pC19 was prevented by the PEPC allosteric effector glucose 6-phosphate (Glc-6P) and by phosphorylation of the enzyme. The role of these elements in the regulation of PEPC proteolysis is discussed in relation to the physiological context.

scholarly journals Relationship between NH+4 Assimilation Rate and in Vivo Phosphoenolpyruvate Carboxylase Activity

1990 ◽  
Vol 94 (1) ◽  
pp. 284-290 ◽  
Author(s):  
Greg C. Vanlerberghe ◽  
Kathryn A. Schuller ◽  
Ronald G. Smith ◽  
Regina Feil ◽  
William C. Plaxton ◽  
...  
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Assimilation Rate ◽  
Carboxylase Activity

scholarly journals Identification of Sequences within the γ-Carboxylase That Represent a Novel Contact Site with Vitamin K-dependent Proteins and That Are Required for Activity

2001 ◽  
Vol 276 (50) ◽  
pp. 46878-46886 ◽  
Author(s):  
B. Nirmala Pudota ◽  
Eric L. Hommema ◽  
Kevin W. Hallgren ◽  
Beth A. McNally ◽  
Susan Lee ◽  
...  
Keyword(s):  
Amino Acids ◽  
Vitamin K ◽  
Complex Analysis ◽  
Factor Ix ◽  
Contact Site ◽  
Carboxylase Activity ◽  
Catalytic Center ◽  
Dependent Protein ◽  
Different Order ◽  
Active Site Conformation

The vitamin K-dependent (VKD) carboxylase converts clusters of Glu residues to γ-carboxylated Glu residues (Glas) in VKD proteins, which is required for their activity. VKD precursors are targeted to the carboxylase by their carboxylase recognition site, which in most cases is a propeptide. We have identified a second tethering site for carboxylase and VKD proteins that is required for carboxylase activity, called the vitamin K-dependent protein site of interaction (VKS). Several VKD proteins specifically bound an immobilized peptide comprising amino acids 343–355 of the human carboxylase (CVYKRSRGKSGQK) but not a scrambled peptide containing the same residues in a different order. Association with the 343–355 peptide was independent of propeptide binding, because the VKD proteins lacked the propeptide and because the 343–355 peptide did not disrupt association of a propeptide factor IX-carboxylase complex. Analysis with peptides that overlapped amino acids 343–355 indicated that the 343–345 CVY residues were necessary but not sufficient for prothrombin binding. Ionic interactions were also suggested because peptide-VKD protein binding could be disrupted by changes in ionic strength or pH. Mutagenesis of Cys343to Ser and Tyr345to Phe resulted in 7–11-fold decreases in vitamin K epoxidation and peptide (EEL) substrate and carboxylase carboxylation, and kinetic analysis showed 5–6-fold increases inKmvalues for the Glu substrate. These results suggest that Cys343and Tyr345are near the catalytic center and affect the active site conformation required for correct positioning of the Glu substrate. The 343–355 VKS peptide had a higher affinity for carboxylated prothrombin (Kd= 5 μm) than uncarboxylated prothrombin (Kd= 60 μm), and the basic VKS region may also facilitate exiting of the Gla product from the catalytic center by ionic attraction. Tethering of VKD proteins to the carboxylase via the propeptide-binding site and the VKS region has important implications for the mechanism of VKD protein carboxylation, and a model is proposed for how the carboxylase VKS region may be required for efficient and processive VKD protein carboxylation.

scholarly journals A study of stabilization of gluconeogenic activity in rat liver slices by calcium and manganese ions

1972 ◽  
Vol 129 (2) ◽  
pp. 231-239 ◽  
Author(s):  
Anne Roobol ◽  
G. A. O. Alleyne
Keyword(s):  
Rat Liver ◽  
Phosphoenolpyruvate Carboxylase ◽  
Incubation Medium ◽  
Lysosomal Enzymes ◽  
Glucose Production ◽  
Liver Slice ◽  
Manganese Ions ◽  
Slice Preparation ◽  
Carboxylase Activity ◽  
Bivalent Cations

1. The effect of some bivalent cations on gluconeogenesis by the rat liver-slice preparation has been investigated. 2. Ca2+and Mn2+stimulated glucose production from a range of substrates but not from glycerol. Mg2+had no effect on the rate of glucose production. 3. Ca2+were required to maintain phosphoenolpyruvate carboxylase activity in the slice preparation. 4. Ca2+and Mn2+, but not Mg2+, retarded the release of lysosomal enzymes from the slice into the incubation medium. 5. It is proposed that Ca2+and Mn2+stimulate glucose production by stabilizing the lysosome system in the liver-slice preparation. 6. The value of the liver-slice preparation as a means of measuring hepatic gluconeogenesis is discussed.

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